diff --git a/basyx/aas/adapter/xml/xml_deserialization.py b/basyx/aas/adapter/xml/xml_deserialization.py
index be66c30c7..8e698cf49 100644
--- a/basyx/aas/adapter/xml/xml_deserialization.py
+++ b/basyx/aas/adapter/xml/xml_deserialization.py
@@ -42,7 +42,7 @@
 """
 
 from ... import model
-from lxml import etree  # type: ignore
+from lxml import etree
 import logging
 import base64
 import enum
@@ -77,7 +77,7 @@ def _str_to_bool(string: str) -> bool:
     return string == "true"
 
 
-def _tag_replace_namespace(tag: str, nsmap: Dict[str, str]) -> str:
+def _tag_replace_namespace(tag: str, nsmap: Dict[Optional[str], str]) -> str:
     """
     Attempts to replace the namespace in front of a tag with the prefix used in the xml document.
 
@@ -92,7 +92,7 @@ def _tag_replace_namespace(tag: str, nsmap: Dict[str, str]) -> str:
     return tag
 
 
-def _element_pretty_identifier(element: etree.Element) -> str:
+def _element_pretty_identifier(element: etree._Element) -> str:
     """
     Returns a pretty element identifier for a given XML element.
 
@@ -129,7 +129,7 @@ def _exception_to_str(exception: BaseException) -> str:
     return string[1:-1] if isinstance(exception, KeyError) else string
 
 
-def _get_child_mandatory(parent: etree.Element, child_tag: str) -> etree.Element:
+def _get_child_mandatory(parent: etree._Element, child_tag: str) -> etree._Element:
     """
     A helper function for getting a mandatory child element.
 
@@ -145,7 +145,7 @@ def _get_child_mandatory(parent: etree.Element, child_tag: str) -> etree.Element
     return child
 
 
-def _get_all_children_expect_tag(parent: etree.Element, expected_tag: str, failsafe: bool) -> Iterable[etree.Element]:
+def _get_all_children_expect_tag(parent: etree._Element, expected_tag: str, failsafe: bool) -> Iterable[etree._Element]:
     """
     Iterates over all children, matching the tag.
 
@@ -168,7 +168,7 @@ def _get_all_children_expect_tag(parent: etree.Element, expected_tag: str, fails
         yield child
 
 
-def _get_attrib_mandatory(element: etree.Element, attrib: str) -> str:
+def _get_attrib_mandatory(element: etree._Element, attrib: str) -> str:
     """
     A helper function for getting a mandatory attribute of an element.
 
@@ -179,10 +179,10 @@ def _get_attrib_mandatory(element: etree.Element, attrib: str) -> str:
     """
     if attrib not in element.attrib:
         raise KeyError(f"{_element_pretty_identifier(element)} has no attribute with name {attrib}!")
-    return element.attrib[attrib]
+    return element.attrib[attrib]  # type: ignore[return-value]
 
 
-def _get_attrib_mandatory_mapped(element: etree.Element, attrib: str, dct: Dict[str, T]) -> T:
+def _get_attrib_mandatory_mapped(element: etree._Element, attrib: str, dct: Dict[str, T]) -> T:
     """
     A helper function for getting a mapped mandatory attribute of an xml element.
 
@@ -203,7 +203,7 @@ def _get_attrib_mandatory_mapped(element: etree.Element, attrib: str, dct: Dict[
     return dct[attrib_value]
 
 
-def _get_text_or_none(element: Optional[etree.Element]) -> Optional[str]:
+def _get_text_or_none(element: Optional[etree._Element]) -> Optional[str]:
     """
     A helper function for getting the text of an element, when it's not clear whether the element exists or not.
 
@@ -219,7 +219,7 @@ def _get_text_or_none(element: Optional[etree.Element]) -> Optional[str]:
     return element.text if element is not None else None
 
 
-def _get_text_mapped_or_none(element: Optional[etree.Element], dct: Dict[str, T]) -> Optional[T]:
+def _get_text_mapped_or_none(element: Optional[etree._Element], dct: Dict[str, T]) -> Optional[T]:
     """
     Returns dct[element.text] or None, if the element is None, has no text or the text is not in dct.
 
@@ -233,7 +233,7 @@ def _get_text_mapped_or_none(element: Optional[etree.Element], dct: Dict[str, T]
     return dct[text]
 
 
-def _get_text_mandatory(element: etree.Element) -> str:
+def _get_text_mandatory(element: etree._Element) -> str:
     """
     A helper function for getting the mandatory text of an element.
 
@@ -247,7 +247,7 @@ def _get_text_mandatory(element: etree.Element) -> str:
     return text
 
 
-def _get_text_mandatory_mapped(element: etree.Element, dct: Dict[str, T]) -> T:
+def _get_text_mandatory_mapped(element: etree._Element, dct: Dict[str, T]) -> T:
     """
     A helper function for getting the mapped mandatory text of an element.
 
@@ -266,7 +266,7 @@ def _get_text_mandatory_mapped(element: etree.Element, dct: Dict[str, T]) -> T:
     return dct[text]
 
 
-def _failsafe_construct(element: Optional[etree.Element], constructor: Callable[..., T], failsafe: bool,
+def _failsafe_construct(element: Optional[etree._Element], constructor: Callable[..., T], failsafe: bool,
                         **kwargs: Any) -> Optional[T]:
     """
     A wrapper function that is used to handle exceptions raised in constructor functions.
@@ -302,7 +302,7 @@ def _failsafe_construct(element: Optional[etree.Element], constructor: Callable[
         return None
 
 
-def _failsafe_construct_mandatory(element: etree.Element, constructor: Callable[..., T], **kwargs: Any) -> T:
+def _failsafe_construct_mandatory(element: etree._Element, constructor: Callable[..., T], **kwargs: Any) -> T:
     """
     _failsafe_construct() but not failsafe and it returns T instead of Optional[T]
 
@@ -320,7 +320,7 @@ def _failsafe_construct_mandatory(element: etree.Element, constructor: Callable[
     return constructed
 
 
-def _failsafe_construct_multiple(elements: Iterable[etree.Element], constructor: Callable[..., T], failsafe: bool,
+def _failsafe_construct_multiple(elements: Iterable[etree._Element], constructor: Callable[..., T], failsafe: bool,
                                  **kwargs: Any) -> Iterable[T]:
     """
     A generator function that applies _failsafe_construct() to multiple elements.
@@ -339,7 +339,7 @@ def _failsafe_construct_multiple(elements: Iterable[etree.Element], constructor:
             yield parsed
 
 
-def _child_construct_mandatory(parent: etree.Element, child_tag: str, constructor: Callable[..., T], **kwargs: Any) \
+def _child_construct_mandatory(parent: etree._Element, child_tag: str, constructor: Callable[..., T], **kwargs: Any) \
         -> T:
     """
     Shorthand for _failsafe_construct_mandatory() in combination with _get_child_mandatory().
@@ -353,7 +353,7 @@ def _child_construct_mandatory(parent: etree.Element, child_tag: str, constructo
     return _failsafe_construct_mandatory(_get_child_mandatory(parent, child_tag), constructor, **kwargs)
 
 
-def _child_construct_multiple(parent: etree.Element, expected_tag: str, constructor: Callable[..., T],
+def _child_construct_multiple(parent: etree._Element, expected_tag: str, constructor: Callable[..., T],
                               failsafe: bool, **kwargs: Any) -> Iterable[T]:
     """
     Shorthand for _failsafe_construct_multiple() in combination with _get_child_multiple().
@@ -370,7 +370,7 @@ def _child_construct_multiple(parent: etree.Element, expected_tag: str, construc
                                         failsafe, **kwargs)
 
 
-def _child_text_mandatory(parent: etree.Element, child_tag: str) -> str:
+def _child_text_mandatory(parent: etree._Element, child_tag: str) -> str:
     """
     Shorthand for _get_text_mandatory() in combination with _get_child_mandatory().
 
@@ -381,7 +381,7 @@ def _child_text_mandatory(parent: etree.Element, child_tag: str) -> str:
     return _get_text_mandatory(_get_child_mandatory(parent, child_tag))
 
 
-def _child_text_mandatory_mapped(parent: etree.Element, child_tag: str, dct: Dict[str, T]) -> T:
+def _child_text_mandatory_mapped(parent: etree._Element, child_tag: str, dct: Dict[str, T]) -> T:
     """
     Shorthand for _get_text_mandatory_mapped() in combination with _get_child_mandatory().
 
@@ -393,7 +393,7 @@ def _child_text_mandatory_mapped(parent: etree.Element, child_tag: str, dct: Dic
     return _get_text_mandatory_mapped(_get_child_mandatory(parent, child_tag), dct)
 
 
-def _get_kind(element: etree.Element) -> model.ModellingKind:
+def _get_kind(element: etree._Element) -> model.ModellingKind:
     """
     Returns the modelling kind of an element with the default value INSTANCE, if none specified.
 
@@ -404,7 +404,7 @@ def _get_kind(element: etree.Element) -> model.ModellingKind:
     return modelling_kind if modelling_kind is not None else model.ModellingKind.INSTANCE
 
 
-def _expect_reference_type(element: etree.Element, expected_type: Type[model.Reference]) -> None:
+def _expect_reference_type(element: etree._Element, expected_type: Type[model.Reference]) -> None:
     """
     Validates the type attribute of a Reference.
 
@@ -430,7 +430,7 @@ class AASFromXmlDecoder:
     stripped = False
 
     @classmethod
-    def _amend_abstract_attributes(cls, obj: object, element: etree.Element) -> None:
+    def _amend_abstract_attributes(cls, obj: object, element: etree._Element) -> None:
         """
         A helper function that amends optional attributes to already constructed class instances, if they inherit
         from an abstract class like Referable, Identifiable, HasSemantics or Qualifiable.
@@ -489,7 +489,7 @@ def _amend_abstract_attributes(cls, obj: object, element: etree.Element) -> None
                     obj.extension.add(extension)
 
     @classmethod
-    def _construct_relationship_element_internal(cls, element: etree.Element, object_class: Type[RE], **_kwargs: Any) \
+    def _construct_relationship_element_internal(cls, element: etree._Element, object_class: Type[RE], **_kwargs: Any) \
             -> RE:
         """
         Helper function used by construct_relationship_element() and construct_annotated_relationship_element()
@@ -504,7 +504,7 @@ def _construct_relationship_element_internal(cls, element: etree.Element, object
         return relationship_element
 
     @classmethod
-    def _construct_key_tuple(cls, element: etree.Element, namespace: str = NS_AAS, **_kwargs: Any) \
+    def _construct_key_tuple(cls, element: etree._Element, namespace: str = NS_AAS, **_kwargs: Any) \
             -> Tuple[model.Key, ...]:
         """
         Helper function used by construct_reference() and construct_aas_reference() to reduce duplicate code
@@ -513,7 +513,7 @@ def _construct_key_tuple(cls, element: etree.Element, namespace: str = NS_AAS, *
         return tuple(_child_construct_multiple(keys, namespace + "key", cls.construct_key, cls.failsafe))
 
     @classmethod
-    def _construct_submodel_reference(cls, element: etree.Element, **kwargs: Any) \
+    def _construct_submodel_reference(cls, element: etree._Element, **kwargs: Any) \
             -> model.ModelReference[model.Submodel]:
         """
         Helper function. Doesn't support the object_class parameter. Overwrite construct_aas_reference instead.
@@ -521,7 +521,7 @@ def _construct_submodel_reference(cls, element: etree.Element, **kwargs: Any) \
         return cls.construct_model_reference_expect_type(element, model.Submodel, **kwargs)
 
     @classmethod
-    def _construct_asset_administration_shell_reference(cls, element: etree.Element, **kwargs: Any) \
+    def _construct_asset_administration_shell_reference(cls, element: etree._Element, **kwargs: Any) \
             -> model.ModelReference[model.AssetAdministrationShell]:
         """
         Helper function. Doesn't support the object_class parameter. Overwrite construct_aas_reference instead.
@@ -529,7 +529,7 @@ def _construct_asset_administration_shell_reference(cls, element: etree.Element,
         return cls.construct_model_reference_expect_type(element, model.AssetAdministrationShell, **kwargs)
 
     @classmethod
-    def _construct_referable_reference(cls, element: etree.Element, **kwargs: Any) \
+    def _construct_referable_reference(cls, element: etree._Element, **kwargs: Any) \
             -> model.ModelReference[model.Referable]:
         """
         Helper function. Doesn't support the object_class parameter. Overwrite construct_aas_reference instead.
@@ -539,7 +539,7 @@ def _construct_referable_reference(cls, element: etree.Element, **kwargs: Any) \
         return cls.construct_model_reference_expect_type(element, model.Referable, **kwargs)  # type: ignore
 
     @classmethod
-    def _construct_operation_variable(cls, element: etree.Element, **kwargs: Any) -> model.SubmodelElement:
+    def _construct_operation_variable(cls, element: etree._Element, **kwargs: Any) -> model.SubmodelElement:
         """
         Since we don't implement ``OperationVariable``, this constructor discards the wrapping `aas:operationVariable`
         and `aas:value` and just returns the contained :class:`~basyx.aas.model.submodel.SubmodelElement`.
@@ -553,7 +553,7 @@ def _construct_operation_variable(cls, element: etree.Element, **kwargs: Any) ->
         return cls.construct_submodel_element(value[0], **kwargs)
 
     @classmethod
-    def construct_key(cls, element: etree.Element, object_class=model.Key, **_kwargs: Any) \
+    def construct_key(cls, element: etree._Element, object_class=model.Key, **_kwargs: Any) \
             -> model.Key:
         return object_class(
             _child_text_mandatory_mapped(element, NS_AAS + "type", KEY_TYPES_INVERSE),
@@ -561,7 +561,7 @@ def construct_key(cls, element: etree.Element, object_class=model.Key, **_kwargs
         )
 
     @classmethod
-    def construct_reference(cls, element: etree.Element, namespace: str = NS_AAS, **kwargs: Any) -> model.Reference:
+    def construct_reference(cls, element: etree._Element, namespace: str = NS_AAS, **kwargs: Any) -> model.Reference:
         reference_type: Type[model.Reference] = _child_text_mandatory_mapped(element, NS_AAS + "type",
                                                                              REFERENCE_TYPES_INVERSE)
         references: Dict[Type[model.Reference], Callable[..., model.Reference]] = {
@@ -573,7 +573,7 @@ def construct_reference(cls, element: etree.Element, namespace: str = NS_AAS, **
         return references[reference_type](element, namespace=namespace, **kwargs)
 
     @classmethod
-    def construct_external_reference(cls, element: etree.Element, namespace: str = NS_AAS,
+    def construct_external_reference(cls, element: etree._Element, namespace: str = NS_AAS,
                                      object_class=model.ExternalReference, **_kwargs: Any) \
             -> model.ExternalReference:
         _expect_reference_type(element, model.ExternalReference)
@@ -582,7 +582,7 @@ def construct_external_reference(cls, element: etree.Element, namespace: str = N
                                                 cls.failsafe, namespace=namespace))
 
     @classmethod
-    def construct_model_reference(cls, element: etree.Element, object_class=model.ModelReference, **_kwargs: Any) \
+    def construct_model_reference(cls, element: etree._Element, object_class=model.ModelReference, **_kwargs: Any) \
             -> model.ModelReference:
         """
         This constructor for ModelReference determines the type of the ModelReference by its keys. If no keys are
@@ -599,7 +599,7 @@ def construct_model_reference(cls, element: etree.Element, object_class=model.Mo
                                                              cls.construct_reference, cls.failsafe))
 
     @classmethod
-    def construct_model_reference_expect_type(cls, element: etree.Element, type_: Type[model.base._RT],
+    def construct_model_reference_expect_type(cls, element: etree._Element, type_: Type[model.base._RT],
                                               object_class=model.ModelReference, **_kwargs: Any) \
             -> model.ModelReference[model.base._RT]:
         """
@@ -616,7 +616,7 @@ def construct_model_reference_expect_type(cls, element: etree.Element, type_: Ty
                                                              cls.construct_reference, cls.failsafe))
 
     @classmethod
-    def construct_administrative_information(cls, element: etree.Element, object_class=model.AdministrativeInformation,
+    def construct_administrative_information(cls, element: etree._Element, object_class=model.AdministrativeInformation,
                                              **_kwargs: Any) -> model.AdministrativeInformation:
         administrative_information = object_class(
             revision=_get_text_or_none(element.find(NS_AAS + "revision")),
@@ -630,7 +630,7 @@ def construct_administrative_information(cls, element: etree.Element, object_cla
         return administrative_information
 
     @classmethod
-    def construct_lang_string_set(cls, element: etree.Element, expected_tag: str, object_class: Type[LSS],
+    def construct_lang_string_set(cls, element: etree._Element, expected_tag: str, object_class: Type[LSS],
                                   **_kwargs: Any) -> LSS:
         collected_lang_strings: Dict[str, str] = {}
         for lang_string_elem in _get_all_children_expect_tag(element, expected_tag, cls.failsafe):
@@ -639,36 +639,36 @@ def construct_lang_string_set(cls, element: etree.Element, expected_tag: str, ob
         return object_class(collected_lang_strings)
 
     @classmethod
-    def construct_multi_language_name_type(cls, element: etree.Element, object_class=model.MultiLanguageNameType,
+    def construct_multi_language_name_type(cls, element: etree._Element, object_class=model.MultiLanguageNameType,
                                            **kwargs: Any) -> model.MultiLanguageNameType:
         return cls.construct_lang_string_set(element, NS_AAS + "langStringNameType", object_class, **kwargs)
 
     @classmethod
-    def construct_multi_language_text_type(cls, element: etree.Element, object_class=model.MultiLanguageTextType,
+    def construct_multi_language_text_type(cls, element: etree._Element, object_class=model.MultiLanguageTextType,
                                            **kwargs: Any) -> model.MultiLanguageTextType:
         return cls.construct_lang_string_set(element, NS_AAS + "langStringTextType", object_class, **kwargs)
 
     @classmethod
-    def construct_definition_type_iec61360(cls, element: etree.Element, object_class=model.DefinitionTypeIEC61360,
+    def construct_definition_type_iec61360(cls, element: etree._Element, object_class=model.DefinitionTypeIEC61360,
                                            **kwargs: Any) -> model.DefinitionTypeIEC61360:
         return cls.construct_lang_string_set(element, NS_AAS + "langStringDefinitionTypeIec61360", object_class,
                                              **kwargs)
 
     @classmethod
-    def construct_preferred_name_type_iec61360(cls, element: etree.Element,
+    def construct_preferred_name_type_iec61360(cls, element: etree._Element,
                                                object_class=model.PreferredNameTypeIEC61360,
                                                **kwargs: Any) -> model.PreferredNameTypeIEC61360:
         return cls.construct_lang_string_set(element, NS_AAS + "langStringPreferredNameTypeIec61360", object_class,
                                              **kwargs)
 
     @classmethod
-    def construct_short_name_type_iec61360(cls, element: etree.Element, object_class=model.ShortNameTypeIEC61360,
+    def construct_short_name_type_iec61360(cls, element: etree._Element, object_class=model.ShortNameTypeIEC61360,
                                            **kwargs: Any) -> model.ShortNameTypeIEC61360:
         return cls.construct_lang_string_set(element, NS_AAS + "langStringShortNameTypeIec61360", object_class,
                                              **kwargs)
 
     @classmethod
-    def construct_qualifier(cls, element: etree.Element, object_class=model.Qualifier, **_kwargs: Any) \
+    def construct_qualifier(cls, element: etree._Element, object_class=model.Qualifier, **_kwargs: Any) \
             -> model.Qualifier:
         qualifier = object_class(
             _child_text_mandatory(element, NS_AAS + "type"),
@@ -687,7 +687,7 @@ def construct_qualifier(cls, element: etree.Element, object_class=model.Qualifie
         return qualifier
 
     @classmethod
-    def construct_extension(cls, element: etree.Element, object_class=model.Extension, **_kwargs: Any) \
+    def construct_extension(cls, element: etree._Element, object_class=model.Extension, **_kwargs: Any) \
             -> model.Extension:
         extension = object_class(
             _child_text_mandatory(element, NS_AAS + "name"))
@@ -706,7 +706,7 @@ def construct_extension(cls, element: etree.Element, object_class=model.Extensio
         return extension
 
     @classmethod
-    def construct_submodel_element(cls, element: etree.Element, **kwargs: Any) -> model.SubmodelElement:
+    def construct_submodel_element(cls, element: etree._Element, **kwargs: Any) -> model.SubmodelElement:
         """
         This function doesn't support the object_class parameter.
         Overwrite each individual SubmodelElement/DataElement constructor function instead.
@@ -726,7 +726,7 @@ def construct_submodel_element(cls, element: etree.Element, **kwargs: Any) -> mo
         return submodel_elements[element.tag](element, **kwargs)
 
     @classmethod
-    def construct_data_element(cls, element: etree.Element, abstract_class_name: str = "DataElement", **kwargs: Any) \
+    def construct_data_element(cls, element: etree._Element, abstract_class_name: str = "DataElement", **kwargs: Any) \
             -> model.DataElement:
         """
         This function does not support the object_class parameter.
@@ -745,7 +745,7 @@ def construct_data_element(cls, element: etree.Element, abstract_class_name: str
         return data_elements[element.tag](element, **kwargs)
 
     @classmethod
-    def construct_annotated_relationship_element(cls, element: etree.Element,
+    def construct_annotated_relationship_element(cls, element: etree._Element,
                                                  object_class=model.AnnotatedRelationshipElement, **_kwargs: Any) \
             -> model.AnnotatedRelationshipElement:
         annotated_relationship_element = cls._construct_relationship_element_internal(element, object_class)
@@ -758,7 +758,7 @@ def construct_annotated_relationship_element(cls, element: etree.Element,
         return annotated_relationship_element
 
     @classmethod
-    def construct_basic_event_element(cls, element: etree.Element, object_class=model.BasicEventElement,
+    def construct_basic_event_element(cls, element: etree._Element, object_class=model.BasicEventElement,
                                       **_kwargs: Any) -> model.BasicEventElement:
         basic_event_element = object_class(
             None,
@@ -786,7 +786,7 @@ def construct_basic_event_element(cls, element: etree.Element, object_class=mode
         return basic_event_element
 
     @classmethod
-    def construct_blob(cls, element: etree.Element, object_class=model.Blob, **_kwargs: Any) -> model.Blob:
+    def construct_blob(cls, element: etree._Element, object_class=model.Blob, **_kwargs: Any) -> model.Blob:
         blob = object_class(
             None,
             _child_text_mandatory(element, NS_AAS + "contentType")
@@ -798,14 +798,14 @@ def construct_blob(cls, element: etree.Element, object_class=model.Blob, **_kwar
         return blob
 
     @classmethod
-    def construct_capability(cls, element: etree.Element, object_class=model.Capability, **_kwargs: Any) \
+    def construct_capability(cls, element: etree._Element, object_class=model.Capability, **_kwargs: Any) \
             -> model.Capability:
         capability = object_class(None)
         cls._amend_abstract_attributes(capability, element)
         return capability
 
     @classmethod
-    def construct_entity(cls, element: etree.Element, object_class=model.Entity, **_kwargs: Any) -> model.Entity:
+    def construct_entity(cls, element: etree._Element, object_class=model.Entity, **_kwargs: Any) -> model.Entity:
         specific_asset_id = set()
         specific_assset_ids = element.find(NS_AAS + "specificAssetIds")
         if specific_assset_ids is not None:
@@ -829,7 +829,7 @@ def construct_entity(cls, element: etree.Element, object_class=model.Entity, **_
         return entity
 
     @classmethod
-    def construct_file(cls, element: etree.Element, object_class=model.File, **_kwargs: Any) -> model.File:
+    def construct_file(cls, element: etree._Element, object_class=model.File, **_kwargs: Any) -> model.File:
         file = object_class(
             None,
             _child_text_mandatory(element, NS_AAS + "contentType")
@@ -841,7 +841,7 @@ def construct_file(cls, element: etree.Element, object_class=model.File, **_kwar
         return file
 
     @classmethod
-    def construct_resource(cls, element: etree.Element, object_class=model.Resource, **_kwargs: Any) -> model.Resource:
+    def construct_resource(cls, element: etree._Element, object_class=model.Resource, **_kwargs: Any) -> model.Resource:
         resource = object_class(
             _child_text_mandatory(element, NS_AAS + "path")
         )
@@ -852,7 +852,7 @@ def construct_resource(cls, element: etree.Element, object_class=model.Resource,
         return resource
 
     @classmethod
-    def construct_multi_language_property(cls, element: etree.Element, object_class=model.MultiLanguageProperty,
+    def construct_multi_language_property(cls, element: etree._Element, object_class=model.MultiLanguageProperty,
                                           **_kwargs: Any) -> model.MultiLanguageProperty:
         multi_language_property = object_class(None)
         value = _failsafe_construct(element.find(NS_AAS + "value"), cls.construct_multi_language_text_type,
@@ -866,7 +866,7 @@ def construct_multi_language_property(cls, element: etree.Element, object_class=
         return multi_language_property
 
     @classmethod
-    def construct_operation(cls, element: etree.Element, object_class=model.Operation, **_kwargs: Any) \
+    def construct_operation(cls, element: etree._Element, object_class=model.Operation, **_kwargs: Any) \
             -> model.Operation:
         operation = object_class(None)
         for tag, target in ((NS_AAS + "inputVariables", operation.input_variable),
@@ -881,7 +881,7 @@ def construct_operation(cls, element: etree.Element, object_class=model.Operatio
         return operation
 
     @classmethod
-    def construct_property(cls, element: etree.Element, object_class=model.Property, **_kwargs: Any) -> model.Property:
+    def construct_property(cls, element: etree._Element, object_class=model.Property, **_kwargs: Any) -> model.Property:
         property_ = object_class(
             None,
             value_type=_child_text_mandatory_mapped(element, NS_AAS + "valueType", model.datatypes.XSD_TYPE_CLASSES)
@@ -896,7 +896,7 @@ def construct_property(cls, element: etree.Element, object_class=model.Property,
         return property_
 
     @classmethod
-    def construct_range(cls, element: etree.Element, object_class=model.Range, **_kwargs: Any) -> model.Range:
+    def construct_range(cls, element: etree._Element, object_class=model.Range, **_kwargs: Any) -> model.Range:
         range_ = object_class(
             None,
             value_type=_child_text_mandatory_mapped(element, NS_AAS + "valueType", model.datatypes.XSD_TYPE_CLASSES)
@@ -911,7 +911,7 @@ def construct_range(cls, element: etree.Element, object_class=model.Range, **_kw
         return range_
 
     @classmethod
-    def construct_reference_element(cls, element: etree.Element, object_class=model.ReferenceElement, **_kwargs: Any) \
+    def construct_reference_element(cls, element: etree._Element, object_class=model.ReferenceElement, **_kwargs: Any) \
             -> model.ReferenceElement:
         reference_element = object_class(None)
         value = _failsafe_construct(element.find(NS_AAS + "value"), cls.construct_reference, cls.failsafe)
@@ -921,12 +921,13 @@ def construct_reference_element(cls, element: etree.Element, object_class=model.
         return reference_element
 
     @classmethod
-    def construct_relationship_element(cls, element: etree.Element, object_class=model.RelationshipElement,
+    def construct_relationship_element(cls, element: etree._Element, object_class=model.RelationshipElement,
                                        **_kwargs: Any) -> model.RelationshipElement:
         return cls._construct_relationship_element_internal(element, object_class=object_class, **_kwargs)
 
     @classmethod
-    def construct_submodel_element_collection(cls, element: etree.Element, object_class=model.SubmodelElementCollection,
+    def construct_submodel_element_collection(cls, element: etree._Element,
+                                              object_class=model.SubmodelElementCollection,
                                               **_kwargs: Any) -> model.SubmodelElementCollection:
         collection = object_class(None)
         if not cls.stripped:
@@ -939,7 +940,7 @@ def construct_submodel_element_collection(cls, element: etree.Element, object_cl
         return collection
 
     @classmethod
-    def construct_submodel_element_list(cls, element: etree.Element, object_class=model.SubmodelElementList,
+    def construct_submodel_element_list(cls, element: etree._Element, object_class=model.SubmodelElementList,
                                         **_kwargs: Any) -> model.SubmodelElementList:
         type_value_list_element = KEY_TYPES_CLASSES_INVERSE[
             _child_text_mandatory_mapped(element, NS_AAS + "typeValueListElement", KEY_TYPES_INVERSE)]
@@ -965,7 +966,7 @@ def construct_submodel_element_list(cls, element: etree.Element, object_class=mo
         return list_
 
     @classmethod
-    def construct_asset_administration_shell(cls, element: etree.Element, object_class=model.AssetAdministrationShell,
+    def construct_asset_administration_shell(cls, element: etree._Element, object_class=model.AssetAdministrationShell,
                                              **_kwargs: Any) -> model.AssetAdministrationShell:
         aas = object_class(
             id_=_child_text_mandatory(element, NS_AAS + "id"),
@@ -986,7 +987,7 @@ def construct_asset_administration_shell(cls, element: etree.Element, object_cla
         return aas
 
     @classmethod
-    def construct_specific_asset_id(cls, element: etree.Element, object_class=model.SpecificAssetId,
+    def construct_specific_asset_id(cls, element: etree._Element, object_class=model.SpecificAssetId,
                                     **_kwargs: Any) -> model.SpecificAssetId:
         # semantic_id can't be applied by _amend_abstract_attributes because specificAssetId is immutable
         return object_class(
@@ -998,7 +999,7 @@ def construct_specific_asset_id(cls, element: etree.Element, object_class=model.
         )
 
     @classmethod
-    def construct_asset_information(cls, element: etree.Element, object_class=model.AssetInformation, **_kwargs: Any) \
+    def construct_asset_information(cls, element: etree._Element, object_class=model.AssetInformation, **_kwargs: Any) \
             -> model.AssetInformation:
         specific_asset_id = set()
         specific_assset_ids = element.find(NS_AAS + "specificAssetIds")
@@ -1025,7 +1026,7 @@ def construct_asset_information(cls, element: etree.Element, object_class=model.
         return asset_information
 
     @classmethod
-    def construct_submodel(cls, element: etree.Element, object_class=model.Submodel, **_kwargs: Any) \
+    def construct_submodel(cls, element: etree._Element, object_class=model.Submodel, **_kwargs: Any) \
             -> model.Submodel:
         submodel = object_class(
             _child_text_mandatory(element, NS_AAS + "id"),
@@ -1041,13 +1042,13 @@ def construct_submodel(cls, element: etree.Element, object_class=model.Submodel,
         return submodel
 
     @classmethod
-    def construct_value_reference_pair(cls, element: etree.Element, object_class=model.ValueReferencePair,
+    def construct_value_reference_pair(cls, element: etree._Element, object_class=model.ValueReferencePair,
                                        **_kwargs: Any) -> model.ValueReferencePair:
         return object_class(_child_text_mandatory(element, NS_AAS + "value"),
                             _child_construct_mandatory(element, NS_AAS + "valueId", cls.construct_reference))
 
     @classmethod
-    def construct_value_list(cls, element: etree.Element, **_kwargs: Any) -> model.ValueList:
+    def construct_value_list(cls, element: etree._Element, **_kwargs: Any) -> model.ValueList:
         """
         This function doesn't support the object_class parameter, because ValueList is just a generic type alias.
         """
@@ -1059,7 +1060,7 @@ def construct_value_list(cls, element: etree.Element, **_kwargs: Any) -> model.V
         )
 
     @classmethod
-    def construct_concept_description(cls, element: etree.Element, object_class=model.ConceptDescription,
+    def construct_concept_description(cls, element: etree._Element, object_class=model.ConceptDescription,
                                       **_kwargs: Any) -> model.ConceptDescription:
         cd = object_class(_child_text_mandatory(element, NS_AAS + "id"))
         is_case_of = element.find(NS_AAS + "isCaseOf")
@@ -1071,7 +1072,8 @@ def construct_concept_description(cls, element: etree.Element, object_class=mode
         return cd
 
     @classmethod
-    def construct_embedded_data_specification(cls, element: etree.Element, object_class=model.EmbeddedDataSpecification,
+    def construct_embedded_data_specification(cls, element: etree._Element,
+                                              object_class=model.EmbeddedDataSpecification,
                                               **_kwargs: Any) -> model.EmbeddedDataSpecification:
         data_specification_content = _get_child_mandatory(element, NS_AAS + "dataSpecificationContent")
         if len(data_specification_content) == 0:
@@ -1087,7 +1089,7 @@ def construct_embedded_data_specification(cls, element: etree.Element, object_cl
         return embedded_data_specification
 
     @classmethod
-    def construct_data_specification_content(cls, element: etree.Element, **kwargs: Any) \
+    def construct_data_specification_content(cls, element: etree._Element, **kwargs: Any) \
             -> model.DataSpecificationContent:
         """
         This function doesn't support the object_class parameter.
@@ -1102,7 +1104,8 @@ def construct_data_specification_content(cls, element: etree.Element, **kwargs:
         return data_specification_contents[element.tag](element, **kwargs)
 
     @classmethod
-    def construct_data_specification_iec61360(cls, element: etree.Element, object_class=model.DataSpecificationIEC61360,
+    def construct_data_specification_iec61360(cls, element: etree._Element,
+                                              object_class=model.DataSpecificationIEC61360,
                                               **_kwargs: Any) -> model.DataSpecificationIEC61360:
         ds_iec = object_class(_child_construct_mandatory(element, NS_AAS + "preferredName",
                                                          cls.construct_preferred_name_type_iec61360))
@@ -1186,7 +1189,7 @@ class StrictStrippedAASFromXmlDecoder(StrictAASFromXmlDecoder, StrippedAASFromXm
     pass
 
 
-def _parse_xml_document(file: PathOrIO, failsafe: bool = True, **parser_kwargs: Any) -> Optional[etree.Element]:
+def _parse_xml_document(file: PathOrIO, failsafe: bool = True, **parser_kwargs: Any) -> Optional[etree._Element]:
     """
     Parse an XML document into an element tree
 
diff --git a/basyx/aas/adapter/xml/xml_serialization.py b/basyx/aas/adapter/xml/xml_serialization.py
index 9d7abfbdf..6f962c8f3 100644
--- a/basyx/aas/adapter/xml/xml_serialization.py
+++ b/basyx/aas/adapter/xml/xml_serialization.py
@@ -15,8 +15,8 @@
   :func:`write_aas_xml_file`.
 - For serializing any object to an XML fragment, that fits the XML specification from 'Details of the
   Asset Administration Shell', chapter 5.4, you can either use :func:`object_to_xml_element`, which serializes a given
-  object and returns it as :class:`~lxml.etree.Element`, **or** :func:`write_aas_xml_element`, which does the same
-  thing, but writes the :class:`~lxml.etree.Element` to a file instead of returning it.
+  object and returns it as :class:`~lxml.etree._Element`, **or** :func:`write_aas_xml_element`, which does the same
+  thing, but writes the :class:`~lxml.etree._Element` to a file instead of returning it.
   As a third alternative, you can also use the functions ``<class_name>_to_xml()`` directly.
 
 .. attention::
@@ -31,7 +31,7 @@
             write_aas_xml_file(fp, object_store)
 """
 
-from lxml import etree  # type: ignore
+from lxml import etree
 from typing import Callable, Dict, Optional, Type
 import base64
 
@@ -47,14 +47,14 @@
 
 def _generate_element(name: str,
                       text: Optional[str] = None,
-                      attributes: Optional[Dict] = None) -> etree.Element:
+                      attributes: Optional[Dict] = None) -> etree._Element:
     """
-    generate an :class:`~lxml.etree.Element` object
+    generate an :class:`~lxml.etree._Element` object
 
     :param name: namespace+tag_name of the element
     :param text: Text of the element. Default is None
     :param attributes: Attributes of the elements in form of a dict ``{"attribute_name": "attribute_content"}``
-    :return: :class:`~lxml.etree.Element` object
+    :return: :class:`~lxml.etree._Element` object
     """
     et_element = etree.Element(name)
     if text:
@@ -83,7 +83,7 @@ def boolean_to_xml(obj: bool) -> str:
 # ##############################################################
 
 
-def abstract_classes_to_xml(tag: str, obj: object) -> etree.Element:
+def abstract_classes_to_xml(tag: str, obj: object) -> etree._Element:
     """
     Generates an XML element and adds attributes of abstract base classes of ``obj``.
 
@@ -151,14 +151,14 @@ def abstract_classes_to_xml(tag: str, obj: object) -> etree.Element:
 
 def _value_to_xml(value: model.ValueDataType,
                   value_type: model.DataTypeDefXsd,
-                  tag: str = NS_AAS+"value") -> etree.Element:
+                  tag: str = NS_AAS+"value") -> etree._Element:
     """
     Serialization of objects of :class:`~basyx.aas.model.base.ValueDataType` to XML
 
     :param value: :class:`~basyx.aas.model.base.ValueDataType` object
     :param value_type: Corresponding :class:`~basyx.aas.model.base.DataTypeDefXsd`
     :param tag: tag of the serialized :class:`~basyx.aas.model.base.ValueDataType` object
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     # todo: add "{NS_XSI+"type": "xs:"+model.datatypes.XSD_TYPE_NAMES[value_type]}" as attribute, if the schema allows
     #  it
@@ -167,13 +167,13 @@ def _value_to_xml(value: model.ValueDataType,
                              text=model.datatypes.xsd_repr(value))
 
 
-def lang_string_set_to_xml(obj: model.LangStringSet, tag: str) -> etree.Element:
+def lang_string_set_to_xml(obj: model.LangStringSet, tag: str) -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.base.LangStringSet` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.base.LangStringSet`
     :param tag: Namespace+Tag name of the returned XML element.
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     LANG_STRING_SET_TAGS: Dict[Type[model.LangStringSet], str] = {k: NS_AAS + v for k, v in {
         model.MultiLanguageNameType: "langStringNameType",
@@ -192,13 +192,13 @@ def lang_string_set_to_xml(obj: model.LangStringSet, tag: str) -> etree.Element:
 
 
 def administrative_information_to_xml(obj: model.AdministrativeInformation,
-                                      tag: str = NS_AAS+"administration") -> etree.Element:
+                                      tag: str = NS_AAS+"administration") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.base.AdministrativeInformation` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.base.AdministrativeInformation`
     :param tag: Namespace+Tag of the serialized element. Default is ``aas:administration``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_administration = abstract_classes_to_xml(tag, obj)
     if obj.version:
@@ -212,12 +212,12 @@ def administrative_information_to_xml(obj: model.AdministrativeInformation,
     return et_administration
 
 
-def data_element_to_xml(obj: model.DataElement) -> etree.Element:
+def data_element_to_xml(obj: model.DataElement) -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.submodel.DataElement` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.submodel.DataElement`
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     if isinstance(obj, model.MultiLanguageProperty):
         return multi_language_property_to_xml(obj)
@@ -231,15 +231,16 @@ def data_element_to_xml(obj: model.DataElement) -> etree.Element:
         return file_to_xml(obj)
     if isinstance(obj, model.ReferenceElement):
         return reference_element_to_xml(obj)
+    raise AssertionError(f"Type {obj.__class__.__name__} is not yet supported by the XML serialization!")
 
 
-def key_to_xml(obj: model.Key, tag: str = NS_AAS+"key") -> etree.Element:
+def key_to_xml(obj: model.Key, tag: str = NS_AAS+"key") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.base.Key` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.base.Key`
     :param tag: Namespace+Tag of the returned element. Default is ``aas:key``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_key = _generate_element(tag)
     et_key.append(_generate_element(name=NS_AAS + "type", text=_generic.KEY_TYPES[obj.type]))
@@ -247,13 +248,13 @@ def key_to_xml(obj: model.Key, tag: str = NS_AAS+"key") -> etree.Element:
     return et_key
 
 
-def reference_to_xml(obj: model.Reference, tag: str = NS_AAS+"reference") -> etree.Element:
+def reference_to_xml(obj: model.Reference, tag: str = NS_AAS+"reference") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.base.Reference` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.base.Reference`
     :param tag: Namespace+Tag of the returned element. Default is ``aas:reference``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_reference = _generate_element(tag)
     et_reference.append(_generate_element(NS_AAS + "type", text=_generic.REFERENCE_TYPES[obj.__class__]))
@@ -267,13 +268,13 @@ def reference_to_xml(obj: model.Reference, tag: str = NS_AAS+"reference") -> etr
     return et_reference
 
 
-def qualifier_to_xml(obj: model.Qualifier, tag: str = NS_AAS+"qualifier") -> etree.Element:
+def qualifier_to_xml(obj: model.Qualifier, tag: str = NS_AAS+"qualifier") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.base.Qualifier` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.base.Qualifier`
     :param tag: Namespace+Tag of the serialized ElementTree object. Default is ``aas:qualifier``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_qualifier = abstract_classes_to_xml(tag, obj)
     et_qualifier.append(_generate_element(NS_AAS + "kind", text=_generic.QUALIFIER_KIND[obj.kind]))
@@ -286,13 +287,13 @@ def qualifier_to_xml(obj: model.Qualifier, tag: str = NS_AAS+"qualifier") -> etr
     return et_qualifier
 
 
-def extension_to_xml(obj: model.Extension, tag: str = NS_AAS+"extension") -> etree.Element:
+def extension_to_xml(obj: model.Extension, tag: str = NS_AAS+"extension") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.base.Extension` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.base.Extension`
     :param tag: Namespace+Tag of the serialized ElementTree object. Default is ``aas:extension``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_extension = abstract_classes_to_xml(tag, obj)
     et_extension.append(_generate_element(NS_AAS + "name", text=obj.name))
@@ -310,13 +311,13 @@ def extension_to_xml(obj: model.Extension, tag: str = NS_AAS+"extension") -> etr
 
 
 def value_reference_pair_to_xml(obj: model.ValueReferencePair,
-                                tag: str = NS_AAS+"valueReferencePair") -> etree.Element:
+                                tag: str = NS_AAS+"valueReferencePair") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.base.ValueReferencePair` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.base.ValueReferencePair`
     :param tag: Namespace+Tag of the serialized element. Default is ``aas:valueReferencePair``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_vrp = _generate_element(tag)
     # TODO: value_type isn't used at all by _value_to_xml(), thus we can ignore the type here for now
@@ -326,7 +327,7 @@ def value_reference_pair_to_xml(obj: model.ValueReferencePair,
 
 
 def value_list_to_xml(obj: model.ValueList,
-                      tag: str = NS_AAS+"valueList") -> etree.Element:
+                      tag: str = NS_AAS+"valueList") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.base.ValueList` to XML
 
@@ -334,7 +335,7 @@ def value_list_to_xml(obj: model.ValueList,
 
     :param obj: Object of class :class:`~basyx.aas.model.base.ValueList`
     :param tag: Namespace+Tag of the serialized element. Default is ``aas:valueList``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_value_list = _generate_element(tag)
     et_value_reference_pairs = _generate_element(NS_AAS+"valueReferencePairs")
@@ -350,13 +351,13 @@ def value_list_to_xml(obj: model.ValueList,
 
 
 def specific_asset_id_to_xml(obj: model.SpecificAssetId, tag: str = NS_AAS + "specifidAssetId") \
-        -> etree.Element:
+        -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.base.SpecificAssetId` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.base.SpecificAssetId`
     :param tag: Namespace+Tag of the ElementTree object. Default is ``aas:identifierKeyValuePair``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_asset_information = abstract_classes_to_xml(tag, obj)
     et_asset_information.append(_generate_element(name=NS_AAS + "name", text=obj.name))
@@ -367,13 +368,13 @@ def specific_asset_id_to_xml(obj: model.SpecificAssetId, tag: str = NS_AAS + "sp
     return et_asset_information
 
 
-def asset_information_to_xml(obj: model.AssetInformation, tag: str = NS_AAS+"assetInformation") -> etree.Element:
+def asset_information_to_xml(obj: model.AssetInformation, tag: str = NS_AAS+"assetInformation") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.aas.AssetInformation` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.aas.AssetInformation`
     :param tag: Namespace+Tag of the ElementTree object. Default is ``aas:assetInformation``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_asset_information = abstract_classes_to_xml(tag, obj)
     et_asset_information.append(_generate_element(name=NS_AAS + "assetKind", text=_generic.ASSET_KIND[obj.asset_kind]))
@@ -393,13 +394,13 @@ def asset_information_to_xml(obj: model.AssetInformation, tag: str = NS_AAS+"ass
 
 
 def concept_description_to_xml(obj: model.ConceptDescription,
-                               tag: str = NS_AAS+"conceptDescription") -> etree.Element:
+                               tag: str = NS_AAS+"conceptDescription") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.concept.ConceptDescription` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.concept.ConceptDescription`
     :param tag: Namespace+Tag of the ElementTree object. Default is ``aas:conceptDescription``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_concept_description = abstract_classes_to_xml(tag, obj)
     if obj.is_case_of:
@@ -411,13 +412,13 @@ def concept_description_to_xml(obj: model.ConceptDescription,
 
 
 def embedded_data_specification_to_xml(obj: model.EmbeddedDataSpecification,
-                                       tag: str = NS_AAS+"embeddedDataSpecification") -> etree.Element:
+                                       tag: str = NS_AAS+"embeddedDataSpecification") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.base.EmbeddedDataSpecification` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.base.EmbeddedDataSpecification`
     :param tag: Namespace+Tag of the ElementTree object. Default is ``aas:embeddedDataSpecification``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_embedded_data_specification = abstract_classes_to_xml(tag, obj)
     et_embedded_data_specification.append(reference_to_xml(obj.data_specification, tag=NS_AAS + "dataSpecification"))
@@ -426,13 +427,13 @@ def embedded_data_specification_to_xml(obj: model.EmbeddedDataSpecification,
 
 
 def data_specification_content_to_xml(obj: model.DataSpecificationContent,
-                                      tag: str = NS_AAS+"dataSpecificationContent") -> etree.Element:
+                                      tag: str = NS_AAS+"dataSpecificationContent") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.base.DataSpecificationContent` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.base.DataSpecificationContent`
     :param tag: Namespace+Tag of the ElementTree object. Default is ``aas:dataSpecificationContent``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_data_specification_content = abstract_classes_to_xml(tag, obj)
     if isinstance(obj, model.DataSpecificationIEC61360):
@@ -443,13 +444,13 @@ def data_specification_content_to_xml(obj: model.DataSpecificationContent,
 
 
 def data_specification_iec61360_to_xml(obj: model.DataSpecificationIEC61360,
-                                       tag: str = NS_AAS+"dataSpecificationIec61360") -> etree.Element:
+                                       tag: str = NS_AAS+"dataSpecificationIec61360") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.base.DataSpecificationIEC61360` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.base.DataSpecificationIEC61360`
     :param tag: Namespace+Tag of the ElementTree object. Default is ``aas:dataSpecificationIec61360``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_data_specification_iec61360 = abstract_classes_to_xml(tag, obj)
     et_data_specification_iec61360.append(lang_string_set_to_xml(obj.preferred_name, NS_AAS + "preferredName"))
@@ -487,13 +488,13 @@ def data_specification_iec61360_to_xml(obj: model.DataSpecificationIEC61360,
 
 
 def asset_administration_shell_to_xml(obj: model.AssetAdministrationShell,
-                                      tag: str = NS_AAS+"assetAdministrationShell") -> etree.Element:
+                                      tag: str = NS_AAS+"assetAdministrationShell") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.aas.AssetAdministrationShell` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.aas.AssetAdministrationShell`
     :param tag: Namespace+Tag of the ElementTree object. Default is ``aas:assetAdministrationShell``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_aas = abstract_classes_to_xml(tag, obj)
     if obj.derived_from:
@@ -512,12 +513,12 @@ def asset_administration_shell_to_xml(obj: model.AssetAdministrationShell,
 # ##############################################################
 
 
-def submodel_element_to_xml(obj: model.SubmodelElement) -> etree.Element:
+def submodel_element_to_xml(obj: model.SubmodelElement) -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.submodel.SubmodelElement` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.submodel.SubmodelElement`
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     if isinstance(obj, model.DataElement):
         return data_element_to_xml(obj)
@@ -537,16 +538,17 @@ def submodel_element_to_xml(obj: model.SubmodelElement) -> etree.Element:
         return submodel_element_collection_to_xml(obj)
     if isinstance(obj, model.SubmodelElementList):
         return submodel_element_list_to_xml(obj)
+    raise AssertionError(f"Type {obj.__class__.__name__} is not yet supported by the XML serialization!")
 
 
 def submodel_to_xml(obj: model.Submodel,
-                    tag: str = NS_AAS+"submodel") -> etree.Element:
+                    tag: str = NS_AAS+"submodel") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.submodel.Submodel` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.submodel.Submodel`
     :param tag: Namespace+Tag of the serialized element (optional). Default is ``aas:submodel``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_submodel = abstract_classes_to_xml(tag, obj)
     if obj.submodel_element:
@@ -558,13 +560,13 @@ def submodel_to_xml(obj: model.Submodel,
 
 
 def property_to_xml(obj: model.Property,
-                    tag: str = NS_AAS+"property") -> etree.Element:
+                    tag: str = NS_AAS+"property") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.submodel.Property` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.submodel.Property`
     :param tag: Namespace+Tag of the serialized element (optional). Default is ``aas:property``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_property = abstract_classes_to_xml(tag, obj)
     et_property.append(_generate_element(NS_AAS + "valueType", text=model.datatypes.XSD_TYPE_NAMES[obj.value_type]))
@@ -576,13 +578,13 @@ def property_to_xml(obj: model.Property,
 
 
 def multi_language_property_to_xml(obj: model.MultiLanguageProperty,
-                                   tag: str = NS_AAS+"multiLanguageProperty") -> etree.Element:
+                                   tag: str = NS_AAS+"multiLanguageProperty") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.submodel.MultiLanguageProperty` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.submodel.MultiLanguageProperty`
     :param tag: Namespace+Tag of the serialized element (optional). Default is ``aas:multiLanguageProperty``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_multi_language_property = abstract_classes_to_xml(tag, obj)
     if obj.value:
@@ -593,13 +595,13 @@ def multi_language_property_to_xml(obj: model.MultiLanguageProperty,
 
 
 def range_to_xml(obj: model.Range,
-                 tag: str = NS_AAS+"range") -> etree.Element:
+                 tag: str = NS_AAS+"range") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.submodel.Range` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.submodel.Range`
     :param tag: Namespace+Tag of the serialized element (optional). Default is ``aas:range``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_range = abstract_classes_to_xml(tag, obj)
     et_range.append(_generate_element(name=NS_AAS + "valueType",
@@ -612,13 +614,13 @@ def range_to_xml(obj: model.Range,
 
 
 def blob_to_xml(obj: model.Blob,
-                tag: str = NS_AAS+"blob") -> etree.Element:
+                tag: str = NS_AAS+"blob") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.submodel.Blob` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.submodel.Blob`
     :param tag: Namespace+Tag of the serialized element. Default is ``aas:blob``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_blob = abstract_classes_to_xml(tag, obj)
     et_value = etree.Element(NS_AAS + "value")
@@ -630,13 +632,13 @@ def blob_to_xml(obj: model.Blob,
 
 
 def file_to_xml(obj: model.File,
-                tag: str = NS_AAS+"file") -> etree.Element:
+                tag: str = NS_AAS+"file") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.submodel.File` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.submodel.File`
     :param tag: Namespace+Tag of the serialized element. Default is ``aas:file``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_file = abstract_classes_to_xml(tag, obj)
     if obj.value:
@@ -646,13 +648,13 @@ def file_to_xml(obj: model.File,
 
 
 def resource_to_xml(obj: model.Resource,
-                    tag: str = NS_AAS+"resource") -> etree.Element:
+                    tag: str = NS_AAS+"resource") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.base.Resource` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.base.Resource`
     :param tag: Namespace+Tag of the serialized element. Default is ``aas:resource``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_resource = abstract_classes_to_xml(tag, obj)
     et_resource.append(_generate_element(NS_AAS + "path", text=obj.path))
@@ -662,13 +664,13 @@ def resource_to_xml(obj: model.Resource,
 
 
 def reference_element_to_xml(obj: model.ReferenceElement,
-                             tag: str = NS_AAS+"referenceElement") -> etree.Element:
+                             tag: str = NS_AAS+"referenceElement") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.submodel.ReferenceElement` to XMl
 
     :param obj: Object of class :class:`~basyx.aas.model.submodel.ReferenceElement`
     :param tag: Namespace+Tag of the serialized element (optional). Default is ``aas:referenceElement``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_reference_element = abstract_classes_to_xml(tag, obj)
     if obj.value:
@@ -677,13 +679,13 @@ def reference_element_to_xml(obj: model.ReferenceElement,
 
 
 def submodel_element_collection_to_xml(obj: model.SubmodelElementCollection,
-                                       tag: str = NS_AAS+"submodelElementCollection") -> etree.Element:
+                                       tag: str = NS_AAS+"submodelElementCollection") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.submodel.SubmodelElementCollection` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.submodel.SubmodelElementCollection`
     :param tag: Namespace+Tag of the serialized element (optional). Default is ``aas:submodelElementCollection``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_submodel_element_collection = abstract_classes_to_xml(tag, obj)
     if obj.value:
@@ -695,13 +697,13 @@ def submodel_element_collection_to_xml(obj: model.SubmodelElementCollection,
 
 
 def submodel_element_list_to_xml(obj: model.SubmodelElementList,
-                                 tag: str = NS_AAS+"submodelElementList") -> etree.Element:
+                                 tag: str = NS_AAS+"submodelElementList") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.submodel.SubmodelElementList` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.submodel.SubmodelElementList`
     :param tag: Namespace+Tag of the serialized element (optional). Default is ``aas:submodelElementList``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_submodel_element_list = abstract_classes_to_xml(tag, obj)
     et_submodel_element_list.append(_generate_element(NS_AAS + "orderRelevant", boolean_to_xml(obj.order_relevant)))
@@ -722,13 +724,13 @@ def submodel_element_list_to_xml(obj: model.SubmodelElementList,
 
 
 def relationship_element_to_xml(obj: model.RelationshipElement,
-                                tag: str = NS_AAS+"relationshipElement") -> etree.Element:
+                                tag: str = NS_AAS+"relationshipElement") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.submodel.RelationshipElement` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.submodel.RelationshipElement`
     :param tag: Namespace+Tag of the serialized element (optional). Default is ``aas:relationshipElement``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_relationship_element = abstract_classes_to_xml(tag, obj)
     et_relationship_element.append(reference_to_xml(obj.first, NS_AAS+"first"))
@@ -737,13 +739,13 @@ def relationship_element_to_xml(obj: model.RelationshipElement,
 
 
 def annotated_relationship_element_to_xml(obj: model.AnnotatedRelationshipElement,
-                                          tag: str = NS_AAS+"annotatedRelationshipElement") -> etree.Element:
+                                          tag: str = NS_AAS+"annotatedRelationshipElement") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.submodel.AnnotatedRelationshipElement` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.submodel.AnnotatedRelationshipElement`
     :param tag: Namespace+Tag of the serialized element (optional): Default is ``aas:annotatedRelationshipElement``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_annotated_relationship_element = relationship_element_to_xml(obj, tag)
     if obj.annotation:
@@ -754,7 +756,7 @@ def annotated_relationship_element_to_xml(obj: model.AnnotatedRelationshipElemen
     return et_annotated_relationship_element
 
 
-def operation_variable_to_xml(obj: model.SubmodelElement, tag: str = NS_AAS+"operationVariable") -> etree.Element:
+def operation_variable_to_xml(obj: model.SubmodelElement, tag: str = NS_AAS+"operationVariable") -> etree._Element:
     """
     Serialization of :class:`~basyx.aas.model.submodel.SubmodelElement` to the XML OperationVariable representation
     Since we don't implement the ``OperationVariable`` class, which is just a wrapper for a single
@@ -763,7 +765,7 @@ def operation_variable_to_xml(obj: model.SubmodelElement, tag: str = NS_AAS+"ope
 
     :param obj: Object of class :class:`~basyx.aas.model.submodel.SubmodelElement`
     :param tag: Namespace+Tag of the serialized element (optional). Default is ``aas:operationVariable``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_operation_variable = _generate_element(tag)
     et_value = _generate_element(NS_AAS+"value")
@@ -773,13 +775,13 @@ def operation_variable_to_xml(obj: model.SubmodelElement, tag: str = NS_AAS+"ope
 
 
 def operation_to_xml(obj: model.Operation,
-                     tag: str = NS_AAS+"operation") -> etree.Element:
+                     tag: str = NS_AAS+"operation") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.submodel.Operation` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.submodel.Operation`
     :param tag: Namespace+Tag of the serialized element (optional). Default is ``aas:operation``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_operation = abstract_classes_to_xml(tag, obj)
     for tag, nss in ((NS_AAS+"inputVariables", obj.input_variable),
@@ -794,25 +796,25 @@ def operation_to_xml(obj: model.Operation,
 
 
 def capability_to_xml(obj: model.Capability,
-                      tag: str = NS_AAS+"capability") -> etree.Element:
+                      tag: str = NS_AAS+"capability") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.submodel.Capability` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.submodel.Capability`
     :param tag: Namespace+Tag of the serialized element, default is ``aas:capability``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     return abstract_classes_to_xml(tag, obj)
 
 
 def entity_to_xml(obj: model.Entity,
-                  tag: str = NS_AAS+"entity") -> etree.Element:
+                  tag: str = NS_AAS+"entity") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.submodel.Entity` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.submodel.Entity`
     :param tag: Namespace+Tag of the serialized element (optional). Default is ``aas:entity``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_entity = abstract_classes_to_xml(tag, obj)
     if obj.statement:
@@ -831,13 +833,13 @@ def entity_to_xml(obj: model.Entity,
     return et_entity
 
 
-def basic_event_element_to_xml(obj: model.BasicEventElement, tag: str = NS_AAS+"basicEventElement") -> etree.Element:
+def basic_event_element_to_xml(obj: model.BasicEventElement, tag: str = NS_AAS+"basicEventElement") -> etree._Element:
     """
     Serialization of objects of class :class:`~basyx.aas.model.submodel.BasicEventElement` to XML
 
     :param obj: Object of class :class:`~basyx.aas.model.submodel.BasicEventElement`
     :param tag: Namespace+Tag of the serialized element (optional). Default is ``aas:basicEventElement``
-    :return: Serialized :class:`~lxml.etree.Element` object
+    :return: Serialized :class:`~lxml.etree._Element` object
     """
     et_basic_event_element = abstract_classes_to_xml(tag, obj)
     et_basic_event_element.append(reference_to_xml(obj.observed, NS_AAS+"observed"))
@@ -863,17 +865,17 @@ def basic_event_element_to_xml(obj: model.BasicEventElement, tag: str = NS_AAS+"
 # general functions
 # ##############################################################
 
-def _write_element(file: _generic.PathOrBinaryIO, element: etree.Element, **kwargs) -> None:
+def _write_element(file: _generic.PathOrBinaryIO, element: etree._Element, **kwargs) -> None:
     etree.ElementTree(element).write(file, encoding="UTF-8", xml_declaration=True, method="xml", **kwargs)
 
 
-def object_to_xml_element(obj: object) -> etree.Element:
+def object_to_xml_element(obj: object) -> etree._Element:
     """
-    Serialize a single object to an :class:`~lxml.etree.Element`.
+    Serialize a single object to an :class:`~lxml.etree._Element`.
 
     :param obj: The object to serialize
     """
-    serialization_func: Callable[..., etree.Element]
+    serialization_func: Callable[..., etree._Element]
 
     if isinstance(obj, model.Key):
         serialization_func = key_to_xml
@@ -958,14 +960,14 @@ def write_aas_xml_element(file: _generic.PathOrBinaryIO, obj: object, **kwargs)
 
     :param file: A filename or file-like object to write the XML-serialized data to
     :param obj: The object to serialize
-    :param kwargs: Additional keyword arguments to be passed to :meth:`~lxml.etree.ElementTree.write`
+    :param kwargs: Additional keyword arguments to be passed to :meth:`~lxml.etree._ElementTree.write`
     """
     return _write_element(file, object_to_xml_element(obj), **kwargs)
 
 
-def object_store_to_xml_element(data: model.AbstractObjectStore) -> etree.Element:
+def object_store_to_xml_element(data: model.AbstractObjectStore) -> etree._Element:
     """
-    Serialize a set of AAS objects to an Asset Administration Shell as :class:`~lxml.etree.Element`.
+    Serialize a set of AAS objects to an Asset Administration Shell as :class:`~lxml.etree._Element`.
     This function is used internally by :meth:`write_aas_xml_file` and shouldn't be
     called directly for most use-cases.
 
@@ -1015,6 +1017,6 @@ def write_aas_xml_file(file: _generic.PathOrBinaryIO,
     :param file: A filename or file-like object to write the XML-serialized data to
     :param data: :class:`ObjectStore <basyx.aas.model.provider.AbstractObjectStore>` which contains different objects of
                  the AAS meta model which should be serialized to an XML file
-    :param kwargs: Additional keyword arguments to be passed to :meth:`~lxml.etree.ElementTree.write`
+    :param kwargs: Additional keyword arguments to be passed to :meth:`~lxml.etree._ElementTree.write`
     """
     return _write_element(file, object_store_to_xml_element(data), **kwargs)
diff --git a/test/adapter/xml/test_xml_deserialization.py b/test/adapter/xml/test_xml_deserialization.py
index aebc3ad3a..8275dc033 100644
--- a/test/adapter/xml/test_xml_deserialization.py
+++ b/test/adapter/xml/test_xml_deserialization.py
@@ -13,7 +13,7 @@
 from basyx.aas.adapter.xml import StrictAASFromXmlDecoder, XMLConstructables, read_aas_xml_file, \
     read_aas_xml_file_into, read_aas_xml_element
 from basyx.aas.adapter._generic import XML_NS_MAP
-from lxml import etree  # type: ignore
+from lxml import etree
 from typing import Iterable, Type, Union
 
 
@@ -434,7 +434,7 @@ def __init__(self, *args, **kwargs):
 
         class EnhancedAASDecoder(StrictAASFromXmlDecoder):
             @classmethod
-            def construct_submodel(cls, element: etree.Element, object_class=EnhancedSubmodel, **kwargs) \
+            def construct_submodel(cls, element: etree._Element, object_class=EnhancedSubmodel, **kwargs) \
                     -> model.Submodel:
                 return super().construct_submodel(element, object_class=object_class, **kwargs)
 
diff --git a/test/adapter/xml/test_xml_serialization.py b/test/adapter/xml/test_xml_serialization.py
index 6d0e544a1..11328f62f 100644
--- a/test/adapter/xml/test_xml_serialization.py
+++ b/test/adapter/xml/test_xml_serialization.py
@@ -8,7 +8,7 @@
 import os
 import unittest
 
-from lxml import etree  # type: ignore
+from lxml import etree
 
 from basyx.aas import model
 from basyx.aas.adapter.xml import write_aas_xml_file, xml_serialization