How to use the gwcs.geometry.CartesianToSpherical function in gwcs

def _tpcorr_init(v2_ref, v3_ref, roll_ref):
        s2c = SphericalToCartesian(name='s2c', wrap_lon_at=180)
        c2s = CartesianToSpherical(name='c2s', wrap_lon_at=180)

        unit_conv = Scale(1.0 / 3600.0, name='arcsec_to_deg_1D')
        unit_conv = unit_conv & unit_conv
        unit_conv.name = 'arcsec_to_deg_2D'

        unit_conv_inv = Scale(3600.0, name='deg_to_arcsec_1D')
        unit_conv_inv = unit_conv_inv & unit_conv_inv
        unit_conv_inv.name = 'deg_to_arcsec_2D'

        affine = AffineTransformation2D(name='tp_affine')
        affine_inv = AffineTransformation2D(name='tp_affine_inv')

        rot = RotationSequence3D(
            [v2_ref, -v3_ref, roll_ref],
            'zyx',
            name='det_to_optic_axis'

try:
    import gwcs
    if LooseVersion(gwcs.__version__) > '0.12.0':
        from gwcs.geometry import CartesianToSpherical, SphericalToCartesian
        _GWCS_VER_GT_0P12 = True
    else:
        _GWCS_VER_GT_0P12 = False

except ImportError:
    _GWCS_VER_GT_0P12 = False


if _GWCS_VER_GT_0P12:
    _S2C = SphericalToCartesian(name='s2c', wrap_lon_at=180)
    _C2S = CartesianToSpherical(name='c2s', wrap_lon_at=180)

else:
    def _S2C(phi, theta):
        phi = np.deg2rad(phi)
        theta = np.deg2rad(theta)
        cs = np.cos(theta)
        x = cs * np.cos(phi)
        y = cs * np.sin(phi)
        z = np.sin(theta)
        return x, y, z

    def _C2S(x, y, z):
        h = np.hypot(x, y)
        phi = np.rad2deg(np.arctan2(y, x))
        theta = np.rad2deg(np.arctan2(z, h))
        return phi, theta

def from_tree_transform(cls, node, ctx):
        transform_type = node['transform_type']
        wrap_lon_at = node['wrap_lon_at']
        if transform_type == 'spherical_to_cartesian':
            return SphericalToCartesian(wrap_lon_at=wrap_lon_at)
        elif transform_type == 'cartesian_to_spherical':
            return CartesianToSpherical(wrap_lon_at=wrap_lon_at)
        else:
            raise TypeError(f"Unknown model_type {transform_type}")

def to_tree_transform(cls, model, ctx):
        if isinstance(model, SphericalToCartesian):
            transform_type = 'spherical_to_cartesian'
        elif isinstance(model, CartesianToSpherical):
            transform_type = 'cartesian_to_spherical'
        else:
            raise TypeError(f"Model of type {model.__class__} is not supported.")

        node = {
            'transform_type': transform_type,
            'wrap_lon_at': model.wrap_lon_at
        }
        return yamlutil.custom_tree_to_tagged_tree(node, ctx)