docs: def submit(self, func, *args, **kwargs):
          """Submit a function for serialized execution on sqs
          """
          self.op_sequence += 1
          self.sqs.send_message(
              QueueUrl=self.map_queue,
              MessageBody=utils.dumps({'args': args, 'kwargs': kwargs}),
              MessageAttributes={
                  'sequence_id': {
                      'StringValue': str(self.op_sequence),
                      'DataType': 'Number'},
                  'op': {
                      'StringValue': named(func),
                      'DataType': 'String',
                  },
                  'ser': {
                      'StringValue': 'json',
                      'DataType': 'String'}}
          )
  
          self.futures[self.op_sequence] = f = SQSFuture(
              self.op_sequence)
          return f