(S / T) -> (S' / T') := fun x => CommaCategory.
Require Import Functor.Core NaturalTransformation.Core. Require Import Functor.Composition.Core NaturalTransformation.Composition.Core. Require Import NaturalTransformation.Composition.Laws. Require Import Functor.Paths. Require Import Category.Strict. Import Comma.Core. Import Functor.Identity.FunctorIdentityNotations NaturalTransformation.Identity.NaturalTransformationIdentityNotations. Require Import HoTT.Tactics PathGroupoids Types.Forall.