proposition: Lemma planar_ecpH : planar ecpH.
proof: Proof. apply: planar_ecpN => //. - exact planar_ecpY. - exact plain_ecpY. - exact cubic_ecpY. exact connected_ecpY. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap geometry color)