public Multimap<DeviceId, VlanId> ignoredVlans() {
        Multimap<DeviceId, VlanId> ignored = ArrayListMultimap.create();

        array.forEach(node -> {
            DeviceId deviceId = DeviceId.deviceId(node.get(DEVICE_ID).asText());
            VlanId vlanId = VlanId.vlanId((short) node.get(VLAN_ID).asInt());
            ignored.put(deviceId, vlanId);
        });

        return ignored;
    }
@Test
    public void testIgnoredDhcpConfig() throws IOException {
        ObjectMapper om = new ObjectMapper();
        JsonNode json = om.readTree(Resources.getResource(CONFIG_FILE_PATH));
        IgnoreDhcpConfig config = new IgnoreDhcpConfig();
        json = json.path("apps").path(DHCP_RELAY_APP).path(IgnoreDhcpConfig.KEY);
        config.init(APP_ID, IgnoreDhcpConfig.KEY, json, om, null);

        assertEquals(2, config.ignoredVlans().size());
        Collection<VlanId> vlanForDev1 = config.ignoredVlans().get(DEV_1_ID);
        Collection<VlanId> vlanForDev2 = config.ignoredVlans().get(DEV_2_ID);

        assertEquals(1, vlanForDev1.size());
        assertEquals(1, vlanForDev2.size());

        assertTrue(vlanForDev1.contains(IGNORED_VLAN));
        assertTrue(vlanForDev2.contains(IGNORED_VLAN));
    }