code: def getBounds(self, tzinfo=None):
          if self.resolution >= datetime.timedelta(days=1) \
          and tzinfo is not None:
              time = self._time.replace(tzinfo=tzinfo)
          else:
              time = self._time
          return (
              min(self.fromDatetime(time), self.fromDatetime(self._time)),
              max(self.fromDatetime(time + self.resolution),
                  self.fromDatetime(self._time + self.resolution))
          )