It is an interesting approach, though I feel like this could introduce some nasty unintended consequences given how dynamic and introspective Python can be (admittedly I haven't studied this particular implementation).

I always treated this a bit like single underscore private functions/methods, i.e., follow a convention that produces code that's easy to reason about, even if it's not strictly enforced by the language/compiler. So in practice this equates to separating out modules that mutate global state, and placing the majority of logic in "strict" modules that only declare a bunch of "pure" classes/routines. So the "non strict" code is really just a thin layer of wiring gluing everything together. For instance my Celery task files tend to be very thin.