code: def aggregations(self):
          
  
          prev_month_start = get_prev_month(self.end, self.query.interval_)
          self.query.since(prev_month_start)
          agg = super().aggregations()
          if agg is None:
              agg = 0  # None is because NaN in ES. Let's convert to 0
          return agg
docs: Get the single valued aggregations with respect to the
          previous time interval.