class_docstr: Stacked Line graph class
docstr: Convert given data values into drawable points (x, y)
  and interpolated points if interpolate option is specified
code: def _points(self, x_pos):
      """
      Convert given data values into drawable points (x, y)
      and interpolated points if interpolate option is specified
      """
      for series_group in (self.series, self.secondary_series):
          accumulation = [0] * self._len
          for serie in series_group[
              :: -1 if self.stack_from_top else 1
          ]:
              accumulation = list(
                  map(sum, zip(accumulation, serie.values))
              )
              serie.points = [
                  (x_pos[i], v) for i, v in enumerate(accumulation)
              ]
              if serie.points and self.interpolate:
                  serie.interpolated = self._interpolate(
                      x_pos, accumulation
                  )
              else:
                  serie.interpolated = []
  
file_path: pygal/pygal/graph/stackedline.py
imports: from pygal.adapters import none_to_zero
  from pygal.graph.line import Line
label_desc: Use image node_id 4 for calling the StackedLine obj's underlying member method code with example usage: obj._points(x_pos) without return types