code: public void clear() {
          CachingWeakRefSubscriber<T> subscriber = manager.get(tag);
          if (subscriber != null) {
              subscriber.clear();
          }
      }
docs: Clears the loader's state. After a configuration change you will no longer received cached
  values and {@link #start(rx.Observable)} will cause the observable to be executed again.
  This is useful if the loader is handling transient state (showing a Toast for example).