code: def _transformBy(self, matrix, **kwargs):
          
          anchor = self.anchor
          bcpIn = absoluteBCPIn(anchor, self.bcpIn)
          bcpOut = absoluteBCPOut(anchor, self.bcpOut)
          points = [bcpIn, anchor, bcpOut]
          t = transform.Transform(*matrix)
          bcpIn, anchor, bcpOut = t.transformPoints(points)
          x, y = anchor
          self._point.x = x
          self._point.y = y
          self.bcpIn = relativeBCPIn(anchor, bcpIn)
          self.bcpOut = relativeBCPOut(anchor, bcpOut)
docs: Subclasses may override this method.