how to tell if it's safe to go from new-style to classic class?

[Terry Reedy]

"Skip Montanaro" <skip at pobox.com> wrote in message
news:16632.467.456578.579424 at montanaro.dyndns.org...
>
> If I have a new-style class what are the restrictions that keep me from
> going back to a classic class?  I know use of __slots__, __new__ or the
> property() builtin make new-style a requirement.  What other constructs
> might the code be using that would prevent me from falling back to use of
> classic classes?

Hmm...
class/staticmethod() ?
__metatype__ stuff
__class__ variable?
__mro__ and any dependencies on the mro change for complicated base-class
sets
type(old-style-class-or-instance)

tjr