proposition: Lemma rwhisker_id_inj {a b : C} (f g : C⟦a, b⟧) (x y : f ==> g) : x ▹ identity b = y ▹ identity b → x = y.
proof: Proof. intro H. apply (vcomp_lcancel (runitor _)). - apply is_invertible_2cell_runitor. - etrans. { apply pathsinv0, vcomp_runitor. } etrans. 2: apply vcomp_runitor. apply maponpaths_2. apply H. Qed.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.CategoryTheory.Core.Categories UniMath.Bicategories.Core.Bicat UniMath.Bicategories.Core.Invertible_2cells UniMath.Bicategories.Core.Examples.OpMorBicat UniMath.Bicategories.Core.Examples.OpCellBicat