proposition: Lemma merge2_add_vlabel (G: graph2) (r: equiv_rel G) x a: merge2 (G [tst x <- a]) r ≃2 merge2 G r [tst \pi x <- a].
proof: Proof. Iso2 (merge_add_vlabel _ _ _); by rewrite merge_add_vlabelE. Defined.
imports: HB(structures) Coq(Setoid Morphisms) mathcomp(all_ssreflect) GraphTheory(edone finite_quotient preliminaries bij equiv) GraphTheory(setoid_bigop structures pttdom mgraph ptt)