> a.intersection(c)
        [Point3D(2, 2, 2)]
        >>> d = Plane(Point3D(6, 0, 0), normal_vector=(2, -5, 3))
        >>> e = Plane(Point3D(2, 0, 0), normal_vector=(3, 4, -3))
        >>> d.intersection(e)
        [Line3D(Point3D(78/23, -24/23, 0), Point3D(147/23, 321/23, 23))]

        r+