proposition: Lemma post_composition_is_functor (A B C : category) (H : [B, C]) : is_functor (post_composition_functor_data A B C H).
proof: Proof. split; simpl in *. - unfold functor_idax . intros. apply post_whisker_identity. - unfold functor_compax . intros. apply post_whisker_composition. 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