@NotNull
    @Override
    Collection<AbstractTreeNode<?>> createChildren(@NotNull Collection<? extends AbstractTreeNode<?>> old) {
      ProjectNode parent = findParent(ProjectNode.class);
      if (parent == null) {
        return Collections.emptyList();
      }
      return parent.createChildren(this, old);
    }
@NotNull
    @Override
    Collection<AbstractTreeNode<?>> createChildren(@NotNull Collection<? extends AbstractTreeNode<?>> old)