code: public EndlessScrollHelper<Model> withNewItemsDeliveredTo(@NonNull ModelAdapter<Model, ?> modelItemAdapter, @NonNull OnNewItemsListener<Model> extraOnNewItemsListener) {
          mOnNewItemsListener = new DeliverToModelAdapter2<>(modelItemAdapter, extraOnNewItemsListener);
          return this;
      }
docs: An overload of {@link #withNewItemsDeliveredTo(ModelAdapter) withNewItemsDeliveredTo()}
  that allows additional callbacks.
  
  @param modelItemAdapter
  @param extraOnNewItemsListener
  @return