public String getDefault(ConfigResource.Type type, String key) {
        ConfigDef configDef = configDefs.get(type);
        if (configDef == null) return null;
        ConfigDef.ConfigKey configKey = configDef.configKeys().get(key);
        if (configKey == null || !configKey.hasDefault()) {
            return null;
        }
        return ConfigDef.convertToString(configKey.defaultValue, configKey.type);
    }
@Test
    public void testGetConfigValueDefault() {
        assertEquals("1", SCHEMA.getDefault(BROKER, "foo.bar"));
        assertNull(SCHEMA.getDefault(BROKER, "foo.baz.quux"));
        assertNull(SCHEMA.getDefault(TOPIC, "abc"));
        assertEquals("true", SCHEMA.getDefault(TOPIC, "ghi"));
    }