code: public PreferencesFx removeEventHandler(EventType<PreferencesFxEvent> eventType,
                                            EventHandler<? super PreferencesFxEvent> eventHandler) {
      preferencesFxModel.removeEventHandler(eventType, eventHandler);
      return this;
    }
docs: Unregisters a previously registered event handler from the model. One handler might have been
  registered for different event types, so the caller needs to specify the particular event type
  from which to unregister the handler.
  
  @param eventType    the event type from which to unregister
  @param eventHandler the handler to unregister
  @throws NullPointerException if either event type or handler are {@code null}.