{A A' B B'} (h : A + B -> A' + B') (Ha : forall a:A, is_inl (h (inl a))) (Hb : forall b:B, is_inr (h (inr b))) `{MapIn O _ _ h} : MapIn O (unfunctor_sum_l h Ha). Proof. intros a. refine (inO_equiv_inO _ (hfiber_unfunctor_sum_l h Ha Hb a)^-1). Defined.
Require Import HoTT.Basics HoTT.Types. Require Import Equiv.BiInv Extensions HProp HFiber NullHomotopy Limits.Pullback. Require Import Homotopy.IdentitySystems. Require Import Colimits.Pushout.