code: def unit_id(self, unit_id=None):
          
          if unit_id is None:
              return self.__unit_id
          if 0 <= int(unit_id) < 256:
              self.__unit_id = int(unit_id)
              return self.__unit_id
          else:
              return None
docs: Get or set unit ID field
  
          :param unit_id: unit ID (0 to 255) or None for get value
          :type unit_id: int or None
          :returns: unit ID or None if set fail
          :rtype: int or None