public <ConfigType extends ConfigInstance> ConfigType toInstance(Class<ConfigType> clazz, String configId) {
        return ConfigInstanceUtil.getNewInstance(clazz, configId, this);
    }
@Test
    public void test_map_of_struct() {
        Slime slime = new Slime();
        Cursor map = slime.setObject().setObject("innermap");
        map.setObject("one").setLong("foo", 1);
        map.setObject("two").setLong("foo", 2);

        MaptypesConfig config = new ConfigPayload(slime).toInstance(MaptypesConfig.class, "");
        assertThat(config.innermap("one").foo(), is(1));
        assertThat(config.innermap("two").foo(), is(2));
    }