code: def _get_separated_values(self, secondary=False):
          
          series = self.secondary_series if secondary else self.series
          transposed = list(zip(*[serie.values for serie in series]))
          positive_vals = [
              sum([val for val in vals if val is not None and val >= self.zero])
              for vals in transposed
          ]
          negative_vals = [
              sum([val for val in vals if val is not None and val < self.zero])
              for vals in transposed
          ]
          return positive_vals, negative_vals
docs: Separate values between positives and negatives stacked