It's not mypy issue. Comparing to TS python typehints (spec wise) are a joke. It's started as bolted on adhoc solution and evolved quite chaotically. For example [1]. TS doesn't require a special decorator (sic!) to make your custom classes to be picked up by type checkers.
Or how make a wrapper function with args and kwargs to pass through?
[1]: https://docs.python.org/3/library/typing.html#typing.datacla...
