Definition op_nt {c d : category} {f g : functor c d} (a : nat_trans f g) : nat_trans (functor_opp g) (functor_opp f). Proof. use tpair. - exact (λ c, a c). - abstract (intros x y h; apply (! (nat_trans_ax a _ _ _ ))). Defined.
Require Import UniMath.Foundations.PartD. Require Import UniMath.Foundations.Propositions. Require Import UniMath.MoreFoundations.All. Require Import UniMath.CategoryTheory.Core.Categories. Require Import UniMath.CategoryTheory.Core.Isos. Require Import UniMath.CategoryTheory.Core.NaturalTransformations. Require Import UniMath.CategoryTheory.Core.Univalence. Require Import UniMath.CategoryTheory.Core.Functors. Require Import UniMath.CategoryTheory.Core.Setcategories. Require Import UniMath.CategoryTheory.FunctorCategory.