docs: def _absolute_template_path(fn):
      """
      Return absolute path for filename from local ``xslt/`` directory.
  
      Args:
          fn (str): Filename. ``MARC21slim2MODS3-4-NDK.xsl`` for example.
  
      Returns:
          str: Absolute path to `fn` in ``xslt`` dicretory..
      """
      return os.path.join(os.path.dirname(__file__), "xslt", fn)