@Override
    public List<URI> services(String protocol, String serviceId, String tag) {
        if(StringUtils.isBlank(serviceId)) {
            logger.debug("The serviceId cannot be blank");
            return new ArrayList<>();
        }

        // transform to a list of URIs
        return discovery(protocol, serviceId, tag).stream()
                .map(this::toUri)
                .collect(Collectors.toList());
    }
@Test
    public void testServices() {
        List<URI> l = cluster.services("http", "com.networknt.apib-1.0.0", null);
        Assert.assertEquals(2, l.size());
    }