code: private void notifyOnPreferenceFragmentHidden(@NonNull final Fragment fragment) {
          for (PreferenceFragmentListener listener : preferenceFragmentListeners) {
              listener.onPreferenceFragmentHidden(fragment);
          }
      }
docs: Notifies all registered listeners that a preference fragment has been hidden.
  
  @param fragment
  The fragment, which has been hidden, as an instance of the class Fragment. The
  fragment may not be null