code: private boolean notifyOnRestoreDefaultValuesRequested() {
          boolean result = true;
  
          for (RestoreDefaultsListener listener : restoreDefaultsListeners) {
              result &= listener.onRestoreDefaultValuesRequested(this);
          }
  
          return result;
      }
docs: Notifies all registered listeners, that the preferences' default values should be restored.
  
  @return True, if restoring the preferences' default values should be proceeded, false
  otherwise