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