docs: def _sd_handler(self, desc_type, unit, desc, show_on_keypad):
          """Text description"""
          if desc_type not in self._descriptions_in_progress:
              LOG.debug("Text description response ignored for " + str(desc_type))
              return
  
          (max_units, results, callback) = self._descriptions_in_progress[desc_type]
          if unit < 0 or unit >= max_units:
              callback(results)
              del self._descriptions_in_progress[desc_type]
              return
  
          results[unit] = desc
          self.send(sd_encode(desc_type=desc_type, unit=unit+1))