code: def _check_warn_threshold(self, time_to, event_dict):
          
          if time_to["total_minutes"] <= self.warn_threshold:
              warn_message = self.py3.safe_format(self.format_notification, event_dict)
              self.py3.notify_user(warn_message, "warning", self.warn_timeout)
docs: Checks if the time until an event starts is less than or equal to the
          warn_threshold. If True, issue a warning with self.py3.notify_user.