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