proposition: Lemma left_unitor_on_id {C : prebicategory} {a : C} : whisker_left (identity1 a) (left_unitor (identity1 a)) = left_unitor (identity1 a ;1; identity1 a).
proof: Proof. use (post_comp_with_z_iso_is_inj (left_unitor (identity1 a))). apply left_unitor_naturality. Defined.
imports: UniMath.Foundations.PartD UniMath.MoreFoundations.Tactics UniMath.CategoryTheory.Core.Categories UniMath.CategoryTheory.Core.Isos UniMath.CategoryTheory.Core.NaturalTransformations UniMath.CategoryTheory.Core.Univalence UniMath.CategoryTheory.Core.Functors UniMath.CategoryTheory.PrecategoryBinProduct UniMath.CategoryTheory.Categories.StandardCategories UniMath.CategoryTheory.HorizontalComposition UniMath.CategoryTheory.Equivalences.Core UniMath.Bicategories.WkCatEnrichment.prebicategory UniMath.Bicategories.WkCatEnrichment.Notations