'Get the name of the key for a super-entity
@param supertable: the super-entity table'

@classmethod
def super_key(cls, supertable, default=None):

    if ((supertable is None) and default):
        return default
    if isinstance(supertable, str):
        supertable = cls.table(supertable)
    try:
        return supertable._id.name
    except AttributeError:
        pass
    raise SyntaxError(('No    id-type    key    found    in    %s' % supertable._tablename))
