The first problem is a valid problem in Python: it essentially don't have a "char" type, instead it only have strings with size 1. This actually ruined type an

The first problem is a valid problem in Python: it essentially don't have a "char" type, instead it only have strings with size 1. This actually ruined type annotation in Python: you can't properly annotate a function to accept anything iterable except string. https://github.com/python/mypy/issues/4334 https://github.com/python/mypy/issues/4334 is a FR to at least check it with mypy.