public Set<Device.Type> deviceTypes() {
        return ImmutableSet.copyOf(getList(DEVICE_TYPES, Device.Type::valueOf, DEFAULT_DEVICE_TYPES));
    }
@Test
    public void testDeviceTypes() {
        Set<Device.Type> inputTypes = new HashSet<Device.Type>() { {
            add(DEVICE_TYPE_1);
            add(DEVICE_TYPE_2);
        } };

        assertNotNull(cfg.deviceTypes(inputTypes));

        Set<Device.Type> outputTypes = cfg.deviceTypes();
        assertTrue(outputTypes.contains(DEVICE_TYPE_1));
        assertTrue(outputTypes.contains(DEVICE_TYPE_2));
        assertEquals(outputTypes.size(), 2);
    }