@staticmethod
def fragment_part(fragment, mark_reverse=False):
    """Return the name of the fragment, or optionally `NAME_r` if the
        fragment is the reverse of another fragment."""
    if hasattr(fragment, 'original_part'):
        name = fragment.original_part.id
    else:
        name = fragment.id
    return name + ('_r' if fragment.is_reversed and mark_reverse else '')
