Lemma isaprop_is_retraction {A B : C} (s : A --> B) (r : B --> A) (H : has_homsets C) : isaprop (is_retraction s r). Proof. apply H. Qed.
Require Import UniMath.Foundations.All. Require Import UniMath.MoreFoundations.All. Require Import UniMath.CategoryTheory.Core.Categories. Require Import UniMath.CategoryTheory.Core.Functors. Require Import UniMath.CategoryTheory.OppositeCategory.Core.