async def add_alternative(self, alt, timeout=OTGW_DEFAULT_TIMEOUT):
        """
        Add the specified Data-ID to the list of alternative commands
        to send to the boiler instead of a Data-ID that is known to be
        unsupported by the boiler. Alternative Data-IDs will always be
        sent to the boiler in a Read-Data request message with the
        data-value set to zero. The table of alternative Data-IDs is
        stored in non-volatile memory so it will persist even if the
        gateway has been powered off. Data-ID values from 1 to 255 are
        allowed.
        Return the ID that was added to the list, or None on failure.

        This method is a coroutine
        """
        cmd = OTGW_CMD_ADD_ALT
        alt = int(alt)
        if alt < 1 or alt > 255:
            return None
        ret = await self._wait_for_cmd(cmd, alt, timeout)
        if ret is not None:
            return int(ret)
Add the specified Data-ID to the list of alternative commands
        to send to the boiler instead of a Data-ID that is known to be
        unsupported by the boiler. Alternative Data-IDs will always be
        sent to the boiler in a Read-Data request message with the
        data-value set to zero. The table of alternative Data-IDs is
        stored in non-volatile memory so it will persist even if the
        gateway has been powered off. Data-ID values from 1 to 255 are
        allowed.
        Return the ID that was added to the list, or None on failure.

        This method is a coroutine