code: def _bar(self, serie, parent, x, y, i, zero, secondary=False):
          
          if secondary:
              cumulation = (
                  self.secondary_negative_cumulation
                  if y < self.zero else self.secondary_positive_cumulation
              )
          else:
              cumulation = (
                  self.negative_cumulation
                  if y < self.zero else self.positive_cumulation
              )
          zero = cumulation[i]
          cumulation[i] = zero + y
          if zero == 0:
              zero = self.zero
              y -= self.zero
          y += zero
  
          width = (self.view.x(1) - self.view.x(0)) / self._len
          x, y = self.view((x, y))
          y = y or 0
          series_margin = width * self._series_margin
          x += series_margin
          width -= 2 * series_margin
          if self.secondary_series:
              width /= 2
              x += int(secondary) * width
              serie_margin = width * self._serie_margin
              x += serie_margin
              width -= 2 * serie_margin
          height = self.view.y(zero) - y
          r = serie.rounded_bars * 1 if serie.rounded_bars else 0
          self.svg.transposable_node(
              parent,
              'rect',
              x=x,
              y=y,
              rx=r,
              ry=r,
              width=width,
              height=height,
              class_='rect reactive tooltip-trigger'
          )
          return x, y, width, height
docs: Internal stacking bar drawing function