How to await inside a dunder method?

I want to make an async database query and insert it inside cls.__setitem__ but of course, I can't use await inside a sync function. how can I tackle this problem?

Async function are really just functions that return something awaitable. Usually a Coroutine for lazy evaluation or a Future or Task for eager evaluation. Here is how I do my async dunder methods:

import asyncio
from collections.abc import Coroutine
from typing import Any


class Foo:
    def __getitem__(self, delay: float) -> Coroutine[Any, Any, str]:
        async def get():
            print("waiting...")
            await asyncio.sleep(delay)
            return "Hello!"
        return get()


async def main():
    foo = Foo()
    print(await foo[1.5])

asyncio.run(main())