fact: Axiom F_pres_weak_pullback_arr: forall (X Y Z:Set) (f:X->Z) (g:Y->Z) (wxy:weak_pullback _ _ _ (lift_F_ _ _ f) (lift_F_ _ _ g)), lift_F_ (weak_pullback _ _ _ f g) X (fun xy=>fst (proj1_sig xy)) (wkpk_id_rht _ _ _ _ _ wxy) = fst (proj1_sig wxy) /\ lift_F_ (weak_pullback _ _ _ f g) Y (fun xy=>snd (proj1_sig xy)) (wkpk_id_rht _ _ _ _ _ wxy) = snd (proj1_sig wxy).
imports: ExtensionalFunctor Setoid