abf a'b'f' : (morphism_sig_T abf a'b'f') <~> morphism abf a'b'f'. Proof. etransitivity; [ | exact (' abf a'b'f') ]. repeat (apply equiv_functor_sigma_id; intro). symmetry; apply equiv_sigma_contr; intro. apply issig_morphism_helper; assumption. Defined.
Require Import HoTT.Basics HoTT.Types. Require Import Functor.Core. Require Import InitialTerminalCategory.Core InitialTerminalCategory.Functors. Require Import Category.Strict. Import Functor.Identity.FunctorIdentityNotations. Module Import CommaCategory.