fact: Variables (G H : graph2) (a: test) (l: pairs (add_vertex2 G a ⊎ H)%G).
imports: HB(structures) Coq(Setoid Morphisms) mathcomp(all_ssreflect) GraphTheory(edone finite_quotient preliminaries bij equiv) GraphTheory(setoid_bigop structures pttdom mgraph mgraph2 rewriting)