code: public RxLoader2<A, B, T> save(SaveCallback<T> saveCallback) {
          super.save(saveCallback);
          return this;
      }
docs: Saves the last value that the {@link rx.Observable} returns in {@link
  rx.Observer#onNext(Object)} in the Activities'ss ore Fragment's instanceState bundle. When
  the {@code Activity} or {@code Fragment} is recreated, then the value will be redelivered.
  
  The value <b>must</b> implement {@link android.os.Parcelable}. If not, you should use {@link
  me.tatarka.rxloader.RxLoader#save(SaveCallback)} to save and restore the value yourself.
  
  @return the {@code RxLoader2} for chaining