Is it possible to get isolines?

[ssquirrel]

First off, thank you very much for this amazing library!

I was trying to highlight isolines and add labels to them just like what you did in this example https://observablehq.com/@fil/contour-labels-svg. Is there a way to get isolines easily? Thanks again.

[Philippe Rivière]

All the contours are isolines; here's an example https://observablehq.com/@fil/tricontour-labels