mypy typing issue: client.aio.models.generate_content_stream requires await twice

[yosupo06]

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Environment details

• Package version: google-genai: 1.1.0 / mypy: 1.15.0

Steps to reproduce

from typing import AsyncGenerator
from google.genai import Client

async def test() -> AsyncGenerator[str | None]:
    client = Client()
    async for chunk in await client.aio.models.generate_content_stream(
        model='gemini-2.0-flash-001', contents='Tell me a story in 300 words.'
    ):
        yield chunk.text

Mypy complains the above code with error: "Awaitable[AsyncIterator[GenerateContentResponse]]" has no attribute "__aiter__"; maybe "__await__"? (not async iterable).

Though the mypy error is resolved by attaching await twice (as the following code), but it doesn't actually work.

    async for chunk in await (await client.aio.models.generate_content_stream(
        model='gemini-2.0-flash-001', contents='Tell me a story in 300 words.'
    )):
        yield chunk.text

I guess the return type of generate_content_stream should be AsyncIterator[types.GenerateContentResponse] instead of Awaitable[AsyncIterator[types.GenerateContentResponse]], but not sure.

Thanks!