diff --git a/nbconvert/exporters/templateexporter.py b/nbconvert/exporters/templateexporter.py
index 0b8c27f41..da932a507 100644
--- a/nbconvert/exporters/templateexporter.py
+++ b/nbconvert/exporters/templateexporter.py
@@ -685,5 +685,3 @@ def _init_resources(self, resources):
 
     def include_tableofcontents(self):
         return True
-        
-        
diff --git a/nbconvert/filters/markdown_mistune.py b/nbconvert/filters/markdown_mistune.py
index c1889f06e..a79ed635e 100644
--- a/nbconvert/filters/markdown_mistune.py
+++ b/nbconvert/filters/markdown_mistune.py
@@ -485,6 +485,7 @@ def render(self, source: str) -> str:
         """Render the HTML output for a Markdown source."""
         return str(super().__call__(source))
 
+
 def markdown2html_mistune(source: str) -> str:
     """Convert a markdown string to HTML using mistune"""
     return MarkdownWithMath(renderer=IPythonRenderer(escape=False)).render(source)
@@ -500,6 +501,7 @@ def heading(self, text, level):
         self.headings.append((level, text))
         return ""  # We return an empty string to avoid outputting the headings
 
+
 def extract_titles_from_markdown_input(markdown_input):
     # Markdown_input is a single string with all the markdown content concatenated
     # Initiate list of titles
@@ -515,12 +517,15 @@ def extract_titles_from_markdown_input(markdown_input):
     extract_titles(markdown_input)
 
     # Extracted headings
-    for level, title in renderer.headings: # renderer.headings is an array for each markdown element
+    for (
+        level,
+        title,
+    ) in renderer.headings:  # renderer.headings is an array for each markdown element
         children = title["children"]
         attrs = title["attrs"]
         raw_text = children[0]["raw"]
         level = attrs["level"]
-        id = raw_text.replace(' ', '-')
-        href= "#" + id
+        id = raw_text.replace(" ", "-")
+        href = "#" + id
         titles_array.append([level, raw_text, id, href])
     return titles_array
diff --git a/share/templates/lab/index.html.j2 b/share/templates/lab/index.html.j2
index b69e7e976..0a313a72f 100644
--- a/share/templates/lab/index.html.j2
+++ b/share/templates/lab/index.html.j2
@@ -186,7 +186,7 @@ a.anchor-link {
 {{text}}
 </a>
 </div>
-{%- endif -%} 
+{%- endif -%}
 {%- if level==2 -%}
 <div class="jp-RenderedHTMLCommon jp-RenderedHTMLTOC-Item-h2">
 <a href={{href}}>
diff --git a/share/templates/lab/static/index.css b/share/templates/lab/static/index.css
index 08224006a..cac2fabab 100644
--- a/share/templates/lab/static/index.css
+++ b/share/templates/lab/static/index.css
@@ -6749,4 +6749,3 @@ div.jp-Cell-Placeholder-content-2 {
 div.jp-Cell-Placeholder-content-3 {
   top: 140px;
 }
-