| 123456789101112131415161718192021 | import asyncioclass handler:    def __init__(self) -> None:        self.__lock = asyncio.Lock()    def __del__(self) -> None:        self.clean()    def open(self) -> None:        pass    async def adding(self, content: str) -> None:        async with self.__lock:            await asyncio.to_thread(self.add, content)    def add(self, content: str) -> None:        raise NotImplementedError()    def clean(self) -> None:        pass
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