code: public static void animate(Widget source, Widget target, Functions.Func callback) {
          animate(source.getElement(), target.getElement(), callback);
      }
docs: Helper method to apply the path animator with callback.
  
  @param source   Source widget to apply the Path Animator
  @param target   Target widget to apply the Path Animator
  @param callback The callback method to be called when the path animator is applied