Definition is_iso' {C : precategory} {b c : C} (f : b --> c) := ∏ a, isweq (postcomp_with f (a:=a)).
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.