@Override
    @SuppressWarnings("unchecked")
    public Collection<String> listService(String namespaceId, String groupName, String selector) throws NacosException {
        Collection<Service> services = ServiceManager.getInstance().getSingletons(namespaceId);
        if (services.isEmpty()) {
            return Collections.EMPTY_LIST;
        }
        // TODO select service by selector
        return selectServiceWithGroupName(services, groupName);
    }
@Test
    void testListService() throws NacosException {
        Collection<String> res = serviceOperatorV2.listService("A", "B", null);
        assertEquals(1, res.size());
    }