proposition: Lemma isaset_iso {C : precategory_data} (hs : has_homsets C) (a b : ob C) : isaset (iso a b).
proof: Proof. change isaset with (isofhlevel 2). apply isofhleveltotal2. - apply hs. - intro f. apply isasetaprop. apply isaprop_is_iso. Qed.
imports: UniMath.Foundations.PartA UniMath.Foundations.Propositions UniMath.Foundations.Sets UniMath.MoreFoundations.Tactics UniMath.CategoryTheory.Core.Categories