class TopologyLinkDataChangeHandler implements DataTreeChangeListener<Link> {

    public ListenerRegistration<TopologyLinkDataChangeHandler> registerAsDataChangeListener() {
        InstanceIdentifier<Link> linkInstance = InstanceIdentifier.builder(NetworkTopology.class)
                .child(Topology.class, new TopologyKey(new TopologyId(topologyId))).child(Link.class).build();
        return dataBroker.registerDataTreeChangeListener(new DataTreeIdentifier<>(
                LogicalDatastoreType.OPERATIONAL, linkInstance), this);
    }

    public  TopologyLinkDataChangeHandler(DataBroker dataBroker, NetworkGraphService networkGraphService);

}