The point is that some (few) attributes should never be cloned, while others should. In this case, I have some objects that are stored through KioukuDB, and it never makes sense that they get the same id as the original object.

I have a role that provides default ids, so it would be nice to have the clone method default to that.

Another thing I need to differentiate is between some attributes that should be shallow clones and others that should be deep clones (using the clone() method on them, of course).