proposition: Theorem first_iso: categories.iso_arrows back forth.
proof: Proof. split. intro. reflexivity. intros ? [? [? ?]]. assumption. Qed.
imports: Coq.Classes.Morphisms Coq.Classes.RelationClasses Coq.Relations.Relation_Definitions Coq.Lists.List MathClasses.interfaces.abstract_algebra MathClasses.interfaces.universal_algebra MathClasses.theory.ua_homomorphisms MathClasses.interfaces.canonical_names MathClasses.theory.ua_subalgebraT MathClasses.misc.util