Function gordon_surface 

pub fn gordon_surface(
    u_curves: &[NurbsCurve],
    v_curves: &[NurbsCurve],
) -> Result<NurbsSurface, GordonRefusal>

The Gordon surface through two crossing curve families, judged against the kernel’s vertex identity band.

See the module documentation for the contract. Use gordon_surface_reported to state the crossing band and read what was measured.