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