fact: Definition is_iso {C : precategory_data} {a b : C} (f : a --> b) := ∏ c, isweq (precomp_with f (c:=c)).
imports: UniMath.Foundations.PartA UniMath.Foundations.Propositions UniMath.Foundations.Sets UniMath.MoreFoundations.Tactics UniMath.CategoryTheory.Core.Categories