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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 add_unknown_id(self, unknown_id, timeout=OTGW_DEFAULT_TIMEOUT):
 """ Inform the gateway that the boiler doesn't support the specified Data-ID, even if the boiler doesn't indicate that by returning an Unknown-DataId response. Using this command allows the gateway to send an alternative Data-ID to the boiler instead. Return the added ID, or None on failure. This method is a coroutine """

        cmd = OTGW_CMD_UNKNOWN_ID
        unknown_id = int(unknown_id)
        if unknown_id < 1 or unknown_id > 255:
            return None
        ret = await self._wait_for_cmd(cmd, unknown_id, timeout)
        if ret is not None:
            return int(ret)