docs: def build_toc_line(toc_line_no_indent: str,
                     no_of_indentation_spaces: int = 0) -> str:
      r"""Build the TOC line.
  
      :parameter toc_line_no_indent: the TOC line without indentation.
      :parameter no_of_indentation_spaces: the number of indentation spaces.
           Defaults to ``0``.
      :type toc_line_no_indent: str
      :type no_of_indentation_spaces: int
      :returns: toc_line, a single line of the table of contents.
      :rtype: str
      :raises: a built-in exception.
      """
      assert no_of_indentation_spaces >= 0
  
      indentation = no_of_indentation_spaces * ' '
      toc_line = indentation + toc_line_no_indent
  
      return toc_line