@classmethod
    def super_key(cls, supertable, default=None):
        """
            Get the name of the key for a super-entity

            @param supertable: the super-entity table
        """

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

    # -------------------------------------------------------------------------
dataset/ETHPy150Open sahana/eden/modules/s3/s3model.py/S3Model.super_key