proposition: Lemma post_whisker_identity (A B : precategory) (C : category) (H : functor B C) (G : functor_data A B) : post_whisker (nat_trans_id G) H = nat_trans_id (functor_composite_data G H).
proof: Proof. apply nat_trans_eq. - apply homset_property. - intro a. unfold post_whisker. simpl. apply functor_id. Qed.
imports: UniMath.Foundations.PartD UniMath.Foundations.Propositions UniMath.Foundations.Sets UniMath.CategoryTheory.Core.Categories UniMath.CategoryTheory.Core.Functors UniMath.CategoryTheory.Core.Isos UniMath.CategoryTheory.Core.NaturalTransformations UniMath.CategoryTheory.FunctorCategory