code: private <X, Y extends AmazonWebServiceRequest> Response<X> invoke(Request<Y> request, HttpResponseHandler<AmazonWebServiceResponse<X>> responseHandler,
              ExecutionContext executionContext) {
  
          return invoke(request, responseHandler, executionContext, null, null);
      }
docs: Normal invoke with authentication. Credentials are required and may be overriden at the request level.