def METHOD_NAME(self, pos):
    points = list(self.point_series)
    if self.angle_snap and len(points):
        # What is the angle between mouse_pos and the last_position?
        p1 = Point(points[-1][0], points[-1][1])
        p2 = Point(pos[0], pos[1])
        oldangle = p1.angle_to(p2)
        dist = p1.distance_to(p2)
        newangle = round(oldangle / tau * 8, 0) / 8 * tau
        p3 = p1.polar(p1, newangle, dist)
        pos = [p3.x, p3.y]
    return pos