@Nullable
    static StatusMark mergeStatus(@Nullable StatusMark one, @Nullable StatusMark another) {
      if (one == null) return another;
      if (another == null) return one;
      if (((MyStatus)one).version > ((MyStatus)another).version) return one;
      return another;
    }
@Nullable
    static StatusMark mergeStatus(@Nullable StatusMark one, @Nullable StatusMark another)