code: public PreferencesFx addEventHandler(EventType<PreferencesFxEvent> eventType,
                                         EventHandler<? super PreferencesFxEvent> eventHandler) {
      preferencesFxModel.addEventHandler(eventType, eventHandler);
      return this;
    }
docs: Registers an event handler with the model. The handler is called when the model receives an
  {@code Event} of the specified type during the bubbling phase of event delivery.
  
  @param eventType    the type of the events to receive by the handler
  @param eventHandler the handler to register
  @throws NullPointerException if either event type or handler are {@code null}.