code: public Future<ChangeMessageVisibilityResult> changeMessageVisibility(ChangeMessageVisibilityRequest request,
                                                  AsyncHandler<ChangeMessageVisibilityRequest, ChangeMessageVisibilityResult> handler) {
          QueueBufferCallback<ChangeMessageVisibilityRequest, ChangeMessageVisibilityResult> callback = null;
          if (handler != null) {
              callback = new QueueBufferCallback<ChangeMessageVisibilityRequest, ChangeMessageVisibilityResult>(handler, request);
          }
  
          QueueBufferFuture<ChangeMessageVisibilityRequest, ChangeMessageVisibilityResult> future =
                  sendBuffer.changeMessageVisibility(request, callback);
          future.setBuffer(this);
          return future;
      }
docs: asynchronously adjust a message's visibility timeout to SQS.
  
  @return a Future object that will be notified when the operation is completed; never null