Send a message of message_type
        :param connection_id: the identity for the connection to send to
        :param message_type: validator_pb2.Message.* enum value
        :param data: bytes serialized protobuf
        :return: future.Future

def send(self, message_type, data, connection_id, callback=None,
             one_way=False):
        """
        Send a message of message_type
        :param connection_id: the identity for the connection to send to
        :param message_type: validator_pb2.Message.* enum value
        :param data: bytes serialized protobuf
        :return: future.Future
        """
        if connection_id not in self._connections:
            raise ValueError("Unknown connection id: {}".format(connection_id))
        connection_info = self._connections.get(connection_id)
        if connection_info.connection_type == \
                ConnectionType.ZMQ_IDENTITY:
            message = validator_pb2.Message(
                correlation_id=_generate_id(),
                content=data,
                message_type=message_type)

            timer_tag = get_enum_name(message.message_type)
            timer_ctx = self._get_send_response_timer(timer_tag).time()
            fut = future.Future(
                message.correlation_id,
                message.content,
                callback,
                timeout=self._connection_timeout,
                timer_ctx=timer_ctx)
            if not one_way:
                self._futures.put(fut)

            self._send_receive_thread.send_message(msg=message,
                                                   connection_id=connection_id)
            return fut

        return connection_info.connection.send(
            message_type,
            data,
            callback=callback,
            one_way=one_way)