proposition: Lemma post_whisker_composition (A B : precategory) (C : category) (H : functor B C) (a b c : functor_data A B) (f : nat_trans a b) (g : nat_trans b c) : post_whisker (nat_trans_comp _ _ _ f g) H = nat_trans_comp _ _ _ (post_whisker f H) (post_whisker g H).
proof: Proof. apply nat_trans_eq. - apply homset_property. - intro; simpl. apply functor_comp. 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