Subclasses may override this method.

def _transformBy(self, matrix, **kwargs):
        """
        Subclasses may override this method.
        """
        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)