modifySelected() and subdivideSelected() aren't working

[TyphaineLeGales]

Hello,
First thanks a lot for these examples and explanations about generative typography.
I'm having some trouble with the code for the 3D fonts.
On the deconstructed example under the //modify selection and //modify selection these lines get me an error message

mesh.modifySelected(new HEM_Extrude().setDistance(4).setRelative(true).setChamfer(0.2), selection);
mesh.subdivideSelected(new HES_CatmullClark(), selection);
mesh.modifySelected(new HEM_VertexExpand().setDistance(6), selection);
mesh.subdivideSelected(new HES_CatmullClark(), selection);

I'm currently working with Processing 3.3.6 and the latest build of the HE_mesh library. I tried checking the changes in the documentation but I'm quite the noob in processing and I couldn't figure it out.

Any help would be great
Thanks