code: def extract_signature(docstring):
      
      root = publish_doctree(docstring, settings_overrides={"report_level": 5})
      fields = get_fields(root)
      return fields.get(SIG_FIELD)
docs: Extract the signature from a docstring.
  
      :sig: (str) -> Optional[str]
      :param docstring: Docstring to extract the signature from.
      :return: Extracted signature, or ``None`` if there's no signature.