docs: private void syncKeyLocked(String key) {
      ApiType obj = this.knownObjects.getByKey(key);
      if (obj == null) {
        return;
      }
  
      String id = this.keyOf(obj);
      Deque<MutablePair<DeltaType, Object>> deltas = this.items.get(id);
      if (deltas != null && !(Collections.isEmptyCollection(deltas))) {
        return;
      }
  
      this.queueActionLocked(DeltaType.Sync, obj);
    }