code: def _get_default_delivery_medium(self):
          
          medium_options = (
              self._conversation.self_conversation_state.delivery_medium_option
          )
          try:
              default_medium = medium_options[0].delivery_medium
          except IndexError:
              logger.warning('Conversation %r has no delivery medium', self.id_)
              default_medium = hangouts_pb2.DeliveryMedium(
                  medium_type=hangouts_pb2.DELIVERY_MEDIUM_BABEL
              )
          for medium_option in medium_options:
              if medium_option.current_default:
                  default_medium = medium_option.delivery_medium
          return default_medium
docs: Return default DeliveryMedium to use for sending messages.
  
          Use the first option, or an option that's marked as the current
          default.