code: async def add_alternative(self, alt, timeout=OTGW_DEFAULT_TIMEOUT):
          
          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)
docs: 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