def METHOD_NAME(self):
    """ Add or remove additional ObserverGraph contributed by the root
    observer. e.g. for handing trait_added event.
    """
    for extra_graph in self.graph.node.iter_extra_graphs(self.graph):
        add_or_remove_notifiers(
            object=self.object,
            graph=extra_graph,
            handler=self.handler,
            target=self.target,
            dispatcher=self.dispatcher,
            remove=self.remove,
        )