def format_diff_xml(a_xml, b_xml):
    """Create a diff between two XML documents.

    Args:
      a_xml: str
      b_xml: str

    Returns:
      str : `Differ`-style delta

    """
    return '\n'.join(
        difflib.ndiff(
            reformat_to_pretty_xml(a_xml).splitlines(),
            reformat_to_pretty_xml(b_xml).splitlines(),
        )
    )
Create a diff between two XML documents.

    Args:
      a_xml: str
      b_xml: str

    Returns:
      str : `Differ`-style delta