async def transaction(
        self,
        func: Callable[["Pipeline"], Union[Any, Awaitable[Any]]],
        *watches: KeyT,
        shard_hint: Optional[str] = None,
        value_from_callable: bool = False,
        watch_delay: Optional[float] = None,
    ):
        """
        Convenience method for executing the callable `func` as a transaction
        while watching all keys specified in `watches`. The 'func' callable
        should expect a single argument which is a Pipeline object.
        """
        pipe: Pipeline
        async with self.pipeline(True, shard_hint) as pipe:
            while True:
                try:
                    if watches:
                        await pipe.watch(*watches)
                    func_value = func(pipe)
                    if inspect.isawaitable(func_value):
                        func_value = await func_value
                    exec_value = await pipe.execute()
                    return func_value if value_from_callable else exec_value
                except WatchError:
                    if watch_delay is not None and watch_delay > 0:
                        await asyncio.sleep(watch_delay)
                    continue

        Convenience method for executing the callable `func` as a transaction
        while watching all keys specified in `watches`. The 'func' callable
        should expect a single argument which is a Pipeline object.
        
aioredis/client.py