def unionstore(self, destination, *others):
        """ The same as :meth:union, but stores the result in @destination

            @destination: #str keyname or :class:RedisSet
            @others: one or several #str keynames or :class:RedisSet objects

            -> #int number of items in the resulting set
        """
        others = self._typesafe_others(others)
        destination = self._typesafe(destination)
        return self._client.sunionstore(destination, self.key_prefix, *others)