proposition: Lemma add_edge_C F x u y z v t: F ∔ [x, u, y] ∔ [z, v, t] ≃ F ∔ [z, v, t] ∔ [x, u, y].
proof: Proof. Iso bij_id option2_swap xpred0. abstract by split; repeat case. Defined.
imports: Coq(Morphisms RelationClasses) mathcomp(all_ssreflect) GraphTheory(edone finite_quotient preliminaries bij) GraphTheory(equiv digraph setoid_bigop structures)