Added deepcopy method to SensorDict (#130)

* Added deepcopy method to SensorDict

* Added typing to __deepcopy__

src/fenicsxconcrete/finite_element_problem/base_material.py

@@ -1,6 +1,9 @@
+from __future__ import annotations
+
 import importlib
 import json
 from abc import ABC, abstractmethod
+from copy import deepcopy
 from dataclasses import dataclass
 from pathlib import Path, PosixPath
 
@@ -239,3 +242,6 @@ def __setitem__(self, initial_key: str, value: BaseSensor) -> None:
                 value.name = key
 
             super().__setitem__(key, value)
+
+        def __deepcopy__(self, memo: dict) -> SensorDict:
+            return self.__class__({k: deepcopy(v, memo) for k, v in self.items()})