@classmethod
    def create_multi(cls, values):
        """Creates multiple unique values at once.

        :param values:
            A sequence of values to be unique. See :meth:`create`.
        :returns:
            A tuple (bool, list_of_keys). If all values were created, bool is
            True and list_of_keys is empty. If one or more values weren't
            created, bool is False and the list contains all the values that
            already existed in datastore during the creation attempt.
        """
        # Maybe do a preliminary check, before going for transactions?
        # entities = model.get_multi(keys)
        # existing = [entity.key.id() for entity in entities if entity]
        # if existing:
        #    return False, existing

        # Create all records transactionally.
        keys = [model.Key(cls, value) for value in values]
        entities = [cls(key=key) for key in keys]
        func = lambda e: e.put() if not e.key.get() else None
        created = [model.transaction(lambda: func(e)) for e in entities]

        if created != keys:
            # A poor man's "rollback": delete all recently created records.
            model.delete_multi(k for k in created if k)
            return False, [k.id() for k in keys if k not in created]

        return True, []
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/webapp2-2.5.1/webapp2_extras/appengine/auth/models.py/Unique.create_multi/original