def config_matcher(segments):
    """A matcher for a mailing list's configuration resource.

    e.g. /config
    e.g. /config/description
    """
    if len(segments) < 1 or segments[0] != 'config':
        return None
    if len(segments) == 1:
        return (), {}, ()
    if len(segments) == 2:
        return (), dict(attribute=segments[1]), ()
    return None
