@Override
  public Boolean isFixedAbstract(M member) {
    final Boolean fixedAbstract1 = myModel1.isFixedAbstract(member);
    if(fixedAbstract1 == null) return null;
    if(fixedAbstract1.equals(myModel2.isFixedAbstract(member))) return fixedAbstract1;
    return null;
  }
@Override
  public Boolean isFixedAbstract(M member)