proposition: Lemma post_whisker_iso_is_iso {B C D : precategory} {G H : functor_data B C} (gamma : nat_trans G H) (K : functor C D) (X : is_nat_iso gamma) : is_nat_iso (post_whisker gamma K).
proof: Proof. intros b. unfold post_whisker. simpl. set ( gammab := make_iso (gamma b) (X b) ). apply (functor_on_iso_is_iso C D K _ _ gammab). Defined.
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