@Override
    public boolean isChildNode(Node child) {
        return nodes.containsKey(child.getUniqueIdentifier());
    }
Returns true if the specified node is a first-level children of this collection
node.

@param child the node to check if it is a direct child of this node.
@return true if the specified node is a first-level children of this collection
        node.
xmppserver/src/main/java/org/jivesoftware/openfire/pubsub/CollectionNode.java