code: def _appendContour(self, contour, offset=None, **kwargs):
          
          copy = contour.copy()
          if offset != (0, 0):
              copy.moveBy(offset)
          pointPen = self.getPointPen()
          contour.drawPoints(pointPen)
          return self[-1]
docs: contour will be an object with a drawPoints method.
  
          offset will be a valid offset (x, y).
  
          This must return the new contour.
  
          Subclasses may override this method.