@Override
    public boolean isCollectionNode() {
        return true;
    }
Returns a collection with the subscriptions to this node that should be notified
that a new child was added or deleted.

@param child the added or deleted child.
@return a collection with the subscriptions to this node that should be notified
        that a new child was added or deleted.
xmppserver/src/main/java/org/jivesoftware/openfire/pubsub/CollectionNode.java