@Override
  public Collection<AbstractTreeNode<?>> getChildrenImpl() {
    ArrayList<AbstractTreeNode<?>> result = new ArrayList<>(getNestedFileNodes());
    Collection<AbstractTreeNode<?>> superChildren = super.getChildrenImpl();
    if (superChildren != null) {
      result.addAll(superChildren);
    }
    return result;
  }
@Override
  public Collection<AbstractTreeNode<?>> getChildrenImpl()