Chris:
Thanx for your reminding.
I think the closure_args is private, so we need to raise attributError in self.get_closure_args() and self.set_closre_args(). Do you agree ?

About setattr(), hmmm, do you mean the setattr() method probably change the closure_args?
I could be wrong, but I think the setattr() method will only affect the method of self, and the items is safe. :)
Please correct me if I misunderstand it :D