proposition: Lemma cface_node_ecpY : cface (node ecpY) (icpY (node x0)).
proof: Proof. by rewrite cface1 cface_icpY connect0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap geometry color)