def _pretty_frame_relation(frel):

    """
    Helper function for pretty-printing a frame relation.

    :param frel: The frame relation to be printed.
    :type frel: AttrDict
    :return: A nicely formated string representation of the frame relation.
    :rtype: str
    """
    outstr = "<{0.type.superFrameName}={0.superFrameName} -- {0.type.name} -> {0.type.subFrameName}={0.subFrameName}>".format(frel)
    return outstr