How to use the aioitertools.itertools.Chain function in aioitertools

"""
        return self.from_iterable(itrs)

    async def from_iterable(self, itrs: AnyIterableIterable[T]) -> AsyncIterator[T]:
        """
        Like chain, but takes an iterable of iterables.

        Alias for chain(*itrs)
        """
        async for itr in iter(itrs):
            async for item in iter(itr):
                yield item


chain = Chain()


async def combinations(itr: AnyIterable[T], r: int) -> AsyncIterator[Tuple[T, ...]]:
    """
    Yield r length subsequences from the given iterable.

    Simple wrapper around itertools.combinations for asyncio.
    This will consume the entire iterable before yielding values.

    Example:

        async for value in combinations(range(4), 3):
            ...  # (0, 1, 2), (0, 1, 3), (0, 2, 3), (1, 2, 3)

    """
    pool: List[T] = await list(itr)