I personally just love Python type hinting for testing purposes. So I can avoid types while prototyping or playing with architecture, but once I have something

I personally just love Python type hinting for testing purposes. So I can avoid types while prototyping or playing with architecture, but once I have something I'm happy with, I find that adding types allows me to gain confidence in the program while having fewer tests, and generally making it easier to refactor further. And full typing is also a great first step for rewriting in another language.