Hierarchical container sorting

I had a problem sorting a tree, by using HierarchicalContainer.sort.

the code of this method is
 

@Override
    protected void doSort() {
        super.doSort();

        Collections.sort(roots, getItemSorter());
        for (LinkedList<Object> childList : children.values()) {
            Collections.sort(childList, getItemSorter());
        }
    }

I do not understand the call to super (so the IndexedContaioner implementation), as it will sort all items, whether or not they do have a 'brother' relation ship.

looks to me more like a bug, as it is completly useless, but I may have miss something.

Thanks