Rust Stream to Python async generator

[jelmer]

While the unstable-streams feature allows converting Python async generators to Rust streams, it would be great if the inverse could also be supported.

[kylebarron]

I think this might be hard to natively support in this library, because you really need to export your own class which can hold the iterator state, but we could improve the documentation on how to do this yourself.

I have an example of this here, where __anext__ polls the next element of the stream.

[jelmer]

Perhaps a macro of same sort to simplify that?

FWIW the README specifically suggests filing a bug about this.

[kylebarron]

I'm just a passive maintainer here (I don't think there's any primary maintainer right now). I think having a macro could be valuable, but I probably don't have enough macro-specific experience to review such a PR myself.