@Override
    public MetadataNode child(String name) {
        try {
            Integer brokerId = Integer.valueOf(name);
            BrokerRegistration registration = image.brokers().get(brokerId);
            if (registration == null) return null;
            return new MetadataLeafNode(registration.toString());
        } catch (NumberFormatException e) {
            return null;
        }
    }
@Test
    public void testUnknownChild() {
        assertNull(NODE.child("2"));
    }