[progressbwc]

It is a pity the type hinting is done in a separate file though, as it leads to a lot of duplication. In this case, I pretty much prefer Python’s approach.

[Lio]

You can still use the inline type hinting from Sorbet. Sorbet is compatible with RBS and you'll probably want to check types via Sorbet anyway.

[nerdponx]

FWIW Python does also support type hinting in separate files, although the use case is mostly in adding annotations to existing code bases.