fact: Definition equiv_iso {C D : Category} {f g : C ⟶ D} : f ≈ g → f ≅[Fun] g := snd (Functor_Setoid_Nat_Iso _ _).
imports: Category.Lib Category.Theory.Category Category.Theory.Isomorphism Category.Theory.Functor Category.Theory.Natural.Transformation Category.Instance.Sets