@Override
  public Object @NotNull [] getChildElements(@NotNull Object element) {
    if (element == myTreeRoot) {
      return myDesigner.getTreeRoots();
    }
    if (element instanceof RadComponent component) {
      return component.getTreeChildren();
    }
    throw new IllegalArgumentException("Unknown element: " + element);
  }
@Override
  public Object @NotNull [] getChildElements(@NotNull Object element)