@Override
    public String lookup(LogEvent event, String key) {
        return Log4j2NacosLoggingPropertiesHolder.getValue(key);
    }
@Test
    void testLookUp() {
        System.setProperty("test.nacos.logging.lookup", "true");
        NacosLoggingProperties properties = new NacosLoggingProperties("", System.getProperties());
        Log4j2NacosLoggingPropertiesHolder.setProperties(properties);
        NacosClientPropertiesLookup nacosClientPropertiesLookup = new NacosClientPropertiesLookup();
        final String actual = nacosClientPropertiesLookup.lookup("test.nacos.logging.lookup");
        assertEquals("true", actual);
    }