Add py.typed file to support mypy typing when installed

[thejaminator]

Hi! I was checking out this repo. Really cool.

I had installed it locally. But when running mypy on the code, i got this error

error: Skipping analyzing "flupy": found module but no type hints or library stubs
note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports

This PR adds the py.typed file to the library such that mypy will analyze the library code.

Or is it intentional to disable mypy analyzing?

noticed that mypy infers map to return Fluent[Any]

from flupy import flu

customers: list[int] = [1, 2, 3]
reveal_type(flu(customers).map(lambda x: x + 1)) # revealed Fluent[Any]

Somehow it can be fixed by changing map signature to

def map(self, func: Callable[[T], _T1], *args: Any, **kwargs: Any) -> "Fluent[_T1]":

On mypy 0.920

[olirice]

Looks great, thank you

[olirice]

I also updated the type for Fluent.map here

Your PR & ^ change are available in "flupy==1.1.8"

Any chance you'd be willing to take a look at Fluent.collect? it currently returns a Collection[T] but I'd love to have it pick up the container type from the container_type argument and return List[T] or Set[T] depending on the callable that gets passed. So far I haven't been able to figure that out.

[thejaminator]

@olirice sure, i'll take a look at it. probably could do it with type bounds :)