diff --git a/nbconvert/exporters/slides.py b/nbconvert/exporters/slides.py
index 62a11402b..e571a90c0 100644
--- a/nbconvert/exporters/slides.py
+++ b/nbconvert/exporters/slides.py
@@ -41,7 +41,7 @@ def preprocess(self, nb, resources=None):
 
         in_fragment = False
 
-        for index, cell in enumerate(nb.cells[first_slide_ix + 1:], start=(first_slide_ix + 1)):
+        for index, cell in enumerate(nb.cells[first_slide_ix + 1 :], start=(first_slide_ix + 1)):
             previous_cell = nb.cells[index - 1]
 
             # Slides are <section> elements in the HTML, subslides (the vertically
diff --git a/nbconvert/filters/ansi.py b/nbconvert/filters/ansi.py
index ac91fc89f..a9882e10e 100644
--- a/nbconvert/filters/ansi.py
+++ b/nbconvert/filters/ansi.py
@@ -197,7 +197,7 @@ def _ansi2anything(text, converter):
                     pass  # Invalid color specification
             else:
                 pass  # Not a color code
-            chunk, text = text[: m.start()], text[m.end():]
+            chunk, text = text[: m.start()], text[m.end() :]
         else:
             chunk, text = text, ""
 
diff --git a/nbconvert/filters/citation.py b/nbconvert/filters/citation.py
index e078ceed0..0db092a42 100644
--- a/nbconvert/filters/citation.py
+++ b/nbconvert/filters/citation.py
@@ -42,7 +42,7 @@ def citation2latex(s):
     outtext = ""
     startpos = 0
     for citation in parser.citelist:
-        outtext += s[startpos: citation[1]]
+        outtext += s[startpos : citation[1]]
         outtext += "\\cite{%s}" % citation[0]
         startpos = citation[2] if len(citation) == 3 else -1
     outtext += s[startpos:] if startpos != -1 else ""
diff --git a/nbconvert/filters/markdown_mistune.py b/nbconvert/filters/markdown_mistune.py
index 44287203e..5f18c9213 100644
--- a/nbconvert/filters/markdown_mistune.py
+++ b/nbconvert/filters/markdown_mistune.py
@@ -14,6 +14,7 @@
 import bs4
 import mistune
 from mistune.renderers.markdown import MarkdownRenderer
+from nbformat import NotebookNode
 from pygments import highlight
 from pygments.formatters import HtmlFormatter
 from pygments.lexer import Lexer
@@ -21,7 +22,6 @@
 from pygments.util import ClassNotFound
 
 from nbconvert.filters.strings import add_anchor
-from nbformat import NotebookNode
 
 try:  # for Mistune >= 3.0
     from mistune import (  # type:ignore[attr-defined]
@@ -386,7 +386,7 @@ def _embed_image_or_attachment(self, src: str) -> str:
 
         attachment_prefix = "attachment:"
         if src.startswith(attachment_prefix):
-            name = src[len(attachment_prefix):]
+            name = src[len(attachment_prefix) :]
 
             if name not in self.attachments:
                 msg = f"missing attachment: {name}"
diff --git a/tests/base.py b/tests/base.py
index d854900a8..ff2bec3d5 100644
--- a/tests/base.py
+++ b/tests/base.py
@@ -176,15 +176,15 @@ def assert_big_text_equal(a, b, chunk_size=80):
     to give better info than vanilla assertEqual for large text blobs.
     """
     for i in range(0, len(a), chunk_size):
-        chunk_a = a[i: i + chunk_size]
-        chunk_b = b[i: i + chunk_size]
+        chunk_a = a[i : i + chunk_size]
+        chunk_b = b[i : i + chunk_size]
         assert chunk_a == chunk_b, "[offset: %i]\n%r != \n%r" % (i, chunk_a, chunk_b)
 
     if len(a) > len(b):
         raise AssertionError(
-            "Length doesn't match (%i > %i). Extra text:\n%r" % (len(a), len(b), a[len(b):])
+            "Length doesn't match (%i > %i). Extra text:\n%r" % (len(a), len(b), a[len(b) :])
         )
     if len(a) < len(b):
         raise AssertionError(
-            "Length doesn't match (%i < %i). Extra text:\n%r" % (len(a), len(b), a[len(b):])
+            "Length doesn't match (%i < %i). Extra text:\n%r" % (len(a), len(b), a[len(b) :])
         )