import asyncio

class 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