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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 async def stop(self) -> None: """Coroutine to stop execution of this server."""

        if not self._is_running:
            raise SublemonRuntimeError(
                'Attempted to stop an already-stopped `Sublemon` instance')

        await self.block()
        self._poll_task.cancel()
        self._is_running = False
        with suppress(asyncio.CancelledError):
            await self._poll_task