def _convert_type(type_):
    """
    Given a ``type_``, convert to a UUID attribute name.
    The empty string converts to ``uuid``.

    :param type_: UUID type
    :type type_: str
    :return: UUID attribute name
    :rtype: str
    """
    if type_ == 'uuid' or type_ == '':
        return 'uuid'
    else:
        return '{0}_uuid'.format(type_)