code: public static <CONTROLLER extends AbstractFXController> Pair<Pane, CONTROLLER> loadFxmlPaneAndControllerPair(final Class<CONTROLLER> controllerClass, final Class clazz, final Callback<Class<?>, Object> controllerFactory) throws CouldNotPerformException {
          return loadFxmlPaneAndControllerPair(loadDefaultFXML(controllerClass), controllerClass, clazz, controllerFactory);
      }
docs: Method load the pane and controller of the given fxml file.
  
  @param controllerClass   the class of the controller.
  @param clazz             the responsible class which is used for class path resolution.
  @param controllerFactory the controller factory to use. Can be null if the default one should be used.
  @param <CONTROLLER>      the type of controller which is controlling the new pane.
  
  @return an pair of the pane and its controller.
  
  @throws CouldNotPerformException is thrown if something went wrong like for example the fxml file does not exist.