proposition: Lemma adj_icpH : {mono icpH : x y / adj x y}.
proof: Proof. by move=> x y; rewrite /icpH adj_icpN adj_icpY !cface_ecpY !andbF !orbF. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap geometry color)