@Override
  public Enumeration<TreePath> getExpandedDescendants(TreePath parent) {
    if (expandImpl != null) {
      return expandImpl.getExpandedDescendants(parent);
    }
    else {
      return super.getExpandedDescendants(parent);
    }
  }
@Override
  public Enumeration<TreePath> getExpandedDescendants(TreePath parent)