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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 turn_off(self, switch=None):
 """Turn off relay."""

        if switch is not None:
            switch = codecs.decode(switch.rjust(2, '0'), 'hex')
            packet = self.protocol.format_packet(b"\x10" + switch + b"\x02")
        else:
            packet = self.protocol.format_packet(b"\x0b")
        states = await self._send(packet)
        return states