docs: def on_date(self, date, only_count=False):
          '''
          Filters out only the rows that match the spectified date.
          Works only on a Result that has _start and _end columns.
  
          :param date: date can be anything Pandas.Timestamp supports parsing
          :param only_count: return back only the match count
          '''
          if not self.check_in_bounds(date):
              raise ValueError('Date %s is not in the queried range.' % date)
          date = Timestamp(date)
          after_start = self._start <= date
          before_end = (self._end > date) | self._end_isnull
          if only_count:
              return np.sum(before_end & after_start)
          else:
              return self.filter(before_end & after_start)