docs: def _daterange(self, recarr, date_range):
          """ Given a recarr, slice out the given artic.date.DateRange if a
          datetime64 index exists """
          idx = self._datetime64_index(recarr)
          if idx and len(recarr):
              dts = recarr[idx]
              mask = Series(np.zeros(len(dts)), index=dts)
              start, end = _start_end(date_range, dts)
              mask[start:end] = 1.0
              return recarr[mask.values.astype(bool)]
          return recarr