svoid metaMapWeakPut(IMeta o, O key, O value) {
  if (o == null || key == null) ret;
  Map map = convertObjectMetaToMap(o);
  synchronized(collectionMutex(map)) {
    Map weakMap = mapGetOrCreate("weak map", () -> syncWeakMap());
    weakMap.put(key, value);
  }
}