code: def _enable_notifications_failed(self, dbus_error):
          
          if ((dbus_error.get_dbus_name() == 'org.bluez.Error.Failed') and
              ((dbus_error.get_dbus_message() == "Already notifying") or
               (dbus_error.get_dbus_message() == "No notify session started"))):
              # Ignore cases where notifications where already enabled or already disabled
              return
          error = _error_from_dbus_error(dbus_error)
          self.service.device.characteristic_enable_notifications_failed(characteristic=self, error=error)
docs: Called when notification enabling has failed.