code: @Override
      public <OUTPUT extends GVRHybridObject, INTER> void registerCallback(
              GVRContext gvrContext, Class<OUTPUT> outClass,
              CancelableCallback<OUTPUT> callback, GVRAndroidResource request,
              int priority) {
          requests.registerCallback(gvrContext, outClass, callback, request,
                  priority);
      }
docs: /*
  The API