docs: public static List<String> metaNamespaceIndexFunc(Object obj) {
      try {
        V1ObjectMeta metadata = Reflect.objectMetadata(obj);
        if (metadata == null) {
          return Collections.emptyList();
        }
        return Collections.singletonList(metadata.getNamespace());
      } catch (ObjectMetaReflectException e) {
        // NOTE(yue9944882): might want to handle this as a checked exception
        throw new RuntimeException(e);
      }
    }