proposition: Lemma baseN_ecpN : fun_base icpN node node (pred2 (Icp x0) (Icp (face (edge (face (edge x0)))))).
proof: Proof. move=> x y; rewrite /= !(inj_eq icpN_inj) -!(canF_eq nodeK). by case/norP=> /negPf-> /negPf->. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap geometry color)