proposition: Lemma nat_α_whisker_left_comp A B C D (F G : A ⟶ B) (H : B ⟶ C) (J : C ⟶ D) (η : F ⟹ G) : to (nat_α G H J) ∙ J ⊳ (H ⊳ η) ≈ (J ◯ H) ⊳ η ∙ to (nat_α F H J).
proof: Proof. simpl; intros; cat. Qed.
imports: Category.Lib Category.Theory.Category Category.Theory.Isomorphism Category.Theory.Functor Category.Theory.Natural.Transformation Category.Instance.Sets