proposition: Lemma left_unit_assoc {X Y Z : C} (g : C⟦Y,Z⟧) (f : C⟦X,Y⟧) : (runitor g) ▻ f = runitor (g ∘ f) o lassociator f g (id₁ Z).
proof: Proof. rewrite <- runitor_triangle. unfold assoc. rewrite vassocr. rewrite lassociator_rassociator. rewrite id2_left. apply idpath. Qed.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.CategoryTheory.Core.Categories UniMath.Bicategories.Core.Bicat UniMath.Bicategories.Core.Invertible_2cells UniMath.Bicategories.Core.Unitors