@Override
  @NotNull
  public List<? extends XValueContainerNode<?>> getLoadedChildren() {
    List<? extends XValueContainerNode<?>> empty = Collections.<XValueGroupNodeImpl>emptyList();
    return ContainerUtil.concat(ObjectUtils.notNull(myTopGroups, empty),
                                ObjectUtils.notNull(myValueChildren, empty),
                                ObjectUtils.notNull(myBottomGroups, empty));
  }
@Override
  @NotNull
  public List<? extends XValueContainerNode<?>> getLoadedChildren()