code: protected void removeAllChildren() {
  
          for (int i = getGroupContainerWidget().getWidgetCount() - 1; i >= 0; i--) {
              Widget widget = getGroupContainerWidget().getWidget(i);
              if (widget instanceof CmsContainerPageElementPanel) {
                  widget.removeFromParent();
              }
          }
      }
docs: Removes all child container elements.<p>