proposition: Lemma oiso2_sym : CRelationClasses.Symmetric oiso2.
proof: Proof. move => F G [isF isG /iso2_sym ?]. by econstructor. 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)