+import java.util.Optional;
+import java.util.function.Consumer;
+import org.opendaylight.mdsal.dom.api.DOMDataTreeChangeListener;
+import org.opendaylight.yangtools.concepts.ListenerRegistration;
+import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
+import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeCandidate;