Send a getmore message and handle the response.

def __send_message(self, operation):
        """Send a getmore message and handle the response.
        """
        client = self.__collection.database.client
        listeners = client._event_listeners
        publish = listeners.enabled_for_commands
        try:
            response = client._send_message_with_response(
                operation, address=self.__address)
        except AutoReconnect:
            # Don't try to send kill cursors on another socket
            # or to another server. It can cause a _pinValue
            # assertion on some server releases if we get here
            # due to a socket timeout.
            self.__killed = True
            raise

        cmd_duration = response.duration
        rqst_id = response.request_id
        from_command = response.from_command

        if publish:
            start = datetime.datetime.now()
        try:
            doc = helpers._unpack_response(response.data,
                                           self.__id,
                                           self.__collection.codec_options)
            if from_command:
                helpers._check_command_response(doc['data'][0])

        except OperationFailure as exc:
            self.__killed = True

            if publish:
                duration = (datetime.datetime.now() - start) + cmd_duration
                listeners.publish_command_failure(
                    duration, exc.details, "getMore", rqst_id, self.__address)

            raise
        except NotMasterError as exc:
            # Don't send kill cursors to another server after a "not master"
            # error. It's completely pointless.
            self.__killed = True

            if publish:
                duration = (datetime.datetime.now() - start) + cmd_duration
                listeners.publish_command_failure(
                    duration, exc.details, "getMore", rqst_id, self.__address)

            client._reset_server_and_request_check(self.address)
            raise
        except Exception as exc:
            if publish:
                duration = (datetime.datetime.now() - start) + cmd_duration
                listeners.publish_command_failure(
                    duration, _convert_exception(exc), "getMore", rqst_id,
                    self.__address)
            raise

        if from_command:
            cursor = doc['data'][0]['cursor']
            documents = cursor['nextBatch']
            self.__id = cursor['id']
            self.__retrieved += len(documents)
        else:
            documents = doc["data"]
            self.__id = doc["cursor_id"]
            self.__retrieved += doc["number_returned"]

        if publish:
            duration = (datetime.datetime.now() - start) + cmd_duration
            # Must publish in getMore command response format.
            res = {"cursor": {"id": self.__id,
                              "ns": self.__collection.full_name,
                              "nextBatch": documents},
                   "ok": 1}
            listeners.publish_command_success(
                duration, res, "getMore", rqst_id, self.__address)

        if self.__id == 0:
            self.__killed = True
        self.__data = deque(documents)