def METHOD_NAME(self, pt1, pt2, pt3):
    """
    >>> pen = SVGPathPen(None)
    >>> pen.curveTo((10, 20), (30, 40), (50, 60))
    >>> pen._commands
    ['C10 20 30 40 50 60']
    """
    pt1 = self.pt(pt1)
    pt2 = self.pt(pt2)
    pt3 = self.pt(pt3)
    t = "C"
    t += pointToString(pt1) + " "
    t += pointToString(pt2) + " "
    t += pointToString(pt3)
    self._commands.append(t)
    self._lastCommand = "C"
    self._lastX, self._lastY = pt3