fact: Definition nat_α {A B C D} (F : A ⟶ B) (G : B ⟶ C) (H : C ⟶ D) : H ◯ (G ◯ F) ≅[Fun] (H ◯ G) ◯ F.
imports: Category.Lib Category.Theory.Category Category.Theory.Isomorphism Category.Theory.Functor Category.Theory.Natural.Transformation Category.Instance.Sets