Definition post_whisker_in_funcat (B C D : category) {G H : [B, C]} (γ : [B, C]⟦G, H⟧) (K : [C, D]) : [B, D]⟦functor_compose G K, functor_compose H K⟧. Proof. exact (post_whisker γ (K: C ⟶ D)). Defined.
Require Import UniMath.Foundations.PartD. Require Import UniMath.Foundations.Propositions. Require Import UniMath.Foundations.Sets. Require Import UniMath.CategoryTheory.Core.Categories. Require Import UniMath.CategoryTheory.Core.Functors. Require Import UniMath.CategoryTheory.Core.Isos. Require Import UniMath.CategoryTheory.Core.NaturalTransformations. Require Import UniMath.CategoryTheory.FunctorCategory.