proposition: Lemma baseN_ecpA : fun_base icpA node node (pred2 (node x0) (face (edge x0))).
proof: Proof. by move=> x y; rewrite /icpA /= /ecpA_node (canF_eq nodeK); do 2?case: ifP. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap geometry color)