fact: Definition postcomp_with {C : precategory_data} {b c : C} (h : b --> c) {a : C} (f : a --> b) : a --> c := f · h.
imports: UniMath.Foundations.PartA UniMath.Foundations.Propositions UniMath.Foundations.Sets UniMath.MoreFoundations.Tactics UniMath.CategoryTheory.Core.Categories