private static Collection<XBreakpointGroup> getGroupNodes(CheckedTreeNode parent) {
    Collection<XBreakpointGroup> nodes = new ArrayList<>();
    Enumeration children = parent.children();
    while (children.hasMoreElements()) {
      Object element = children.nextElement();
      if (element instanceof BreakpointsGroupNode) {
        nodes.add(((BreakpointsGroupNode<?>)element).getGroup());
      }
    }
    return nodes;
  }
private static Collection<XBreakpointGroup> getGroupNodes(CheckedTreeNode parent)