Fix type hint on `Subscriber.__aiter__`

[wookie184]

I've read the contributing guidelines and believe this is clear enough to open an issue directly. I might open a PR at some point but if someone else can get to it first please do!

Current type hint: https://github.com/encode/broadcaster/blob/23c9b40136231d0a78d1299588b62d7162067ff4/broadcaster/_base.py#L113 Incorrect complaint by pyright cause by this:

Correct type hint:

async def __aiter__(self) -> AsyncGenerator[Event, None]: 

Or the also correct and a bit nicer (and consistent with Broadcast.subscribe):

async def __aiter__(self) -> AsyncIterator[Event]:

[alex-oleshkevich]

It is a generator because it yield's.

[wookie184]

collections.abc.AsyncGenerator inherits from collections.abc.AsyncIterator, so you can use the more generic AsyncIterator if you aren't using any generator-specific functionality (like sending values to the generator). This is mentioned in the typing docs here.

I mentioned it because it's already used for the async generator a few lines above. Either option is fine though: https://github.com/encode/broadcaster/blob/23c9b40136231d0a78d1299588b62d7162067ff4/broadcaster/_base.py#L90

[alexandreseris]

If you prefer keep the generator type, I think you can just change the return type of Subscriber.__aiter__ to AsyncGenerator[Event, None], since __iter__ never return None and its value are also never None but plain Event.

That should resolve the error wookie184 described

[alex-oleshkevich]

Merged.