Lemma is_univalent_REL : is_univalent REL. Proof. intros X Y. use weqhomot. - exact (bin_hrel_z_iso_equiv_hset_z_iso X Y ∘ make_weq _ (is_univalent_HSET X Y))%weq. - intro p ; induction p. use (z_iso_eq (C := REL)). do 2 (apply funextsec ; intro). apply idpath. Qed.
Require Import UniMath.Foundations.All. Require Import UniMath.MoreFoundations.All. Require Import UniMath.CategoryTheory.Core.Categories. Require Import UniMath.CategoryTheory.Core.Isos. Require Import UniMath.CategoryTheory.Core.Univalence. Require Import UniMath.CategoryTheory.Categories.HSET.All.