sinterface IMeta {
  // see class "Meta" for the bla bla
  
  public void _setMeta(O meta);
  public O _getMeta();
  default public IAutoCloseableF0 _tempMetaMutex() {
    ret new IAutoCloseableF0 {
      public O get() { ret IMeta.this; }
      public void close {}
    };
  }
  
  // actually query another object
  default public O metaGet aka getMeta(O obj, O key) {
    // call global function
    ret metaMapGet(obj, key);
  }
  
  default public O metaGet(S key, O obj) {
    // call global function
    ret metaMapGet(obj, key);
  }
  
  default public O metaGet aka getMeta(O key) {
    if (key == null) null;
    O meta = _getMeta();
    if (meta cast Map) ret meta.get(key);
    null;
  }
  
  default public void metaPut aka metaSet(IMeta obj, O key, O value) {
    // call global function
    metaMapPut(obj, key, value);
  }
  
  default public void metaPut aka metaSet(O key, O value) {
    if (key == null) ret;
    Map map = convertObjectMetaToMap(this);
    syncMapPutOrRemove(map, key, value);
  }
}