proposition: Lemma add_edge2_iso F G (h: F ≃2 G) x u y: F ∔ [x, u, y] ≃2 G ∔ [h x, u, h y].
proof: Proof. by apply add_edge2_iso'. Defined.
imports: HB(structures) Coq(Setoid Morphisms) mathcomp(all_ssreflect) GraphTheory(edone finite_quotient preliminaries bij equiv) GraphTheory(setoid_bigop structures pttdom mgraph ptt)