Section about_isIso.
Variables (A B : Category) (F G : Functor A B) (T : NT F G).
(* qq a. Ta isIso => T isIso *)
Variable h : forall a : A, G a --> F a.
Hypothesis H : forall a : A, AreIsos (T a) (h a).
Canonical Structure NTinv := Build_NT NTinv_nt_law.
Canonical Structure NT_Iso : NatIso F G := NT_areIso.
(* T isIso => qq a. Ta isIso *)
Variable T1 : NT G F.
Hypothesis H' : AreNatIsos T T1.
Variable a : A.

Lemma NTa_areIso : AreIsos (T a) (T1 a).