docs: def format_diff_pyxb(a_pyxb, b_pyxb):
      """Create a diff between two PyXB objects.
  
      Args:
        a_pyxb: PyXB object
        b_pyxb: PyXB object
  
      Returns:
        str : `Differ`-style delta
  
      """
      return '\n'.join(
          difflib.ndiff(
              serialize_to_xml_str(a_pyxb).splitlines(),
              serialize_to_xml_str(b_pyxb).splitlines(),
          )
      )