有人告訴我下面的代碼是不安全的，因為它不允許有一個從 nursery 內(nèi)部產(chǎn)生的異步生成器，除非它是一個異步上下文管理器。T = TypeVar('T')async def delay(interval: float, source: AsyncIterable[T]) -> AsyncIterable[T]:    """Delays each item in source by an interval.    Received items are temporarily stored in an unbounded queue, along with a timestamp, using    a background task. The foreground task takes items from the queue, and waits until the    item is older than the given interval and then yields it."""    send_channel, receive_channel = trio.open_memory_channel(math.inf)    async def pull_task():        async with aclosing(source) as agen:            async for item in agen:                send_channel.send_nowait((item, trio.current_time() + interval))    async with trio.open_nursery() as nursery:        nursery.start_soon(pull_task)        async with receive_channel:            async for item, timestamp in receive_channel:                now = trio.current_time()                if timestamp > now:                    await trio.sleep(timestamp - now)                yield item我很難理解這怎么可能會破裂。如果有人可以提供使用這個確切的生成器函數(shù)的示例代碼，它證明了不安全性，我們將不勝感激和獎勵。上述代碼的目標(biāo)是在不施加任何背壓的情況下延遲異步序列的處理。如果您能證明此代碼無法像我預(yù)期的那樣工作，那我們也將不勝感激。