proposition: Lemma fconnect_sumf_lr x y : fconnect sumf (inl x) (inr y) = false.
proof: Proof. apply/negbTE/negP => /connectP[p]. elim: p x => //= -[x|//] p IHp z /andP[_]; exact: IHp. Qed.
imports: mathcomp(all_ssreflect) GraphTheory(edone preliminaries bij) fourcolor(hypermap geometry cfmap jordan color coloring combinatorial4ct) fourcolor(walkup)