docs: def _bucket_time(self, event_time):
      """
      The seconds since epoch that represent a computed bucket.
  
      An event bucket is the time of the earliest possible event for
      that `bucket_width`.  Example: if `bucket_width =
      timedelta(minutes=10)`, bucket times will be the number of seconds
      since epoch at 12:00, 12:10, ...  on each day.
      """
      event_time = kronos_time_to_epoch_time(event_time)
      return event_time - (event_time % self._bucket_width)