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