proposition: Lemma planar_WalkupF : planar G -> planar WalkupF.
proof: Proof. by rewrite /planar genus_permN -(genus_permF G) => /planar_WalkupE->. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap)