@Override
    protected void deletingNode() {
        // Update child nodes to use the parent node of this node as the new parent node
        final CollectionNode parent = getParent();
        for (Node node : getNodes()) {
            node.changeParent(parent);
        }
    }
Notification that a child node was deleted from this node. Trigger notifications
to node subscribers whose subscription type is {@link NodeSubscription.Type#nodes} and
have the proper depth.

@param child the deleted node that was removed from this node.
xmppserver/src/main/java/org/jivesoftware/openfire/pubsub/CollectionNode.java