code: public <T extends BaseResult> HttpResponseHandler<T> createResponseHandler(
              JsonOperationMetadata operationMetadata,
              Unmarshaller<T, JsonUnmarshallerContext> responseUnmarshaller) {
          final JsonResponseHandler<T> responseHandler = JSON_FACTORY
                  .createResponseHandler(operationMetadata, responseUnmarshaller);
          return new ApiGatewayResponseHandler<>(responseHandler);
      }
docs: Creates a response handler to be used for handling a successful response.
  
  @param operationMetadata Additional context information about an operation to create the appropriate response handler.