fact: Definition open_add_vertex a : open (G ∔ a) ⩭2 (open G) ∔ [fresh (vset (open G)), a].
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)