proposition: Lemma disp_functor_ff_inv_identity {x : C} (xx : D x) : disp_functor_ff_inv (transportb _ (functor_id F _ ) (id_disp (FF _ xx))) = id_disp xx.
proof: Proof. apply invmap_eq. apply pathsinv0. apply (disp_functor_id FF). Qed.
imports: UniMath.Foundations.Sets UniMath.MoreFoundations.PartA UniMath.CategoryTheory.Core.Categories UniMath.CategoryTheory.Core.Functors UniMath.CategoryTheory.Core.Isos UniMath.CategoryTheory.DisplayedCats.Core UniMath.CategoryTheory.DisplayedCats.Isos