@Contract("_, true->!null")
  private static Timestamps getTimestamp(int id, boolean createIfNoneSaved) {
    assert id > 0;
    Timestamps timestamps = ourTimestampsCache.get(id);
    if (timestamps == null) {
      TimestampsImmutable immutable = storage.invoke().readTimestamps(id);
      if (immutable == null) {
        if (createIfNoneSaved) {
          timestamps = new Timestamps();
        }
        else {
          return null;
        }
      }
      else {
        timestamps = immutable.toMutableTimestamps();
      }
    }
    ourTimestampsCache.cacheOrGet(id, timestamps);
    return timestamps;
  }
@Contract("_, true->!null")
  private static Timestamps getTimestamp(int id, boolean createIfNoneSaved)