It appears lambdas are not triggered from items being pushed to SQS if [SendMessageBatch](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/APIReference/API_SendMessageBatch.html) is used instead of [SendMessage](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/APIReference/API_SendMessage.html)
def forward_request(self, method, path, data, headers):
                records.append(data)
                return 200
        records = []
        local_port = get_free_tcp_port()
        proxy = start_proxy(local_port, backend_url=None, update_listener=MyUpdateListener())
        items_before = len(records)
        _run_forward_to_fallback_url('%s://localhost:%s' % (get_service_protocol(), local_port))
        items_after = len(records)
        self.assertEqual(items_after, items_before + 3)
        proxy.stop()
    def test_dead_letter_queue(self):
        sqs_client = aws_stack.connect_to_service('sqs')
        lambda_client = aws_stack.connect_to_service('lambda')
        
        queue_name = 'test-%s' % short_uid()
        lambda_name = 'test-%s' % short_uid()
        queue_url = sqs_client.create_queue(QueueName=queue_name)['QueueUrl']
        queue_arn = aws_stack.sqs_queue_arn(queue_name)
        testutil.create_lambda_function(
            handler_file=TEST_LAMBDA_PYTHON, func_name=lambda_name, libs=TEST_LAMBDA_LIBS,
            runtime=LAMBDA_RUNTIME_PYTHON36, DeadLetterConfig={'TargetArn': queue_arn})
        
        payload = {
            lambda_integration.MSG_BODY_RAISE_ERROR_FLAG: 1
        }
        lambda_client.invoke(FunctionName=lambda_name,
            Payload=json.dumps(payload), InvocationType='Event')
        
        def receive_dlq():