class_docstr: A filter pen to convert cubic bezier curves to quadratic b-splines
  using the FontTools SegmentPen protocol.
  
  Args:
  
      other_pen: another SegmentPen used to draw the transformed outline.
      max_err: maximum approximation error in font units. For optimal results,
          if you know the UPEM of the font, we recommend setting this to a
          value equal, or close to UPEM / 1000.
      reverse_direction: flip the contours' direction but keep starting point.
      stats: a dictionary counting the point numbers of quadratic segments.
      all_quadratic: if True (default), only quadratic b-splines are generated.
          if False, quadratic curves or cubic curves are generated depending
          on which one is more economical.
code: def _convert_curve(self, pt1, pt2, pt3):
      curve = (self.current_pt, pt1, pt2, pt3)
      result = curve_to_quadratic(
          curve, self.max_err, self.all_quadratic
      )
      if self.stats is not None:
          n = str(len(result) - 2)
          self.stats[n] = self.stats.get(n, 0) + 1
      if self.all_quadratic:
          self.qCurveTo(*result[1:])
      else:
          if len(result) == 3:
              self.qCurveTo(*result[1:])
          else:
              assert len(result) == 4
              super().curveTo(*result[1:])
  
imports: import operator
  from fontTools.cu2qu import curve_to_quadratic, curves_to_quadratic
  from fontTools.pens.basePen import decomposeSuperBezierSegment
  from fontTools.pens.filterPen import FilterPen
  from fontTools.pens.reverseContourPen import ReverseContourPen
  from fontTools.pens.pointPen import BasePointToSegmentPen
  from fontTools.pens.pointPen import ReverseContourPointPen
label_desc: Use image node_id 2 for calling the Cu2QuPen obj's underlying member method code with example usage: obj._convert_curve(pt1, pt2, pt3) without return types