proposition: Lemma vset_add_vertex (G : pre_graph) x a z : z \in vset (G ∔ [x,a]) = (z == x) || (z \in vset G).
proof: Proof. by rewrite /= !inE. Qed.
imports: Coq(Relation_Definitions Morphisms RelationClasses) mathcomp(all_ssreflect) GraphTheory(edone finite_quotient preliminaries bij equiv) GraphTheory(setoid_bigop structures pttdom mgraph mgraph2) GraphTheory(rewriting open_confluence finmap_plus)