proposition: Corollary inr_left {x y z : C} (f : x ~> y) : left f ∘ @inr x z ≈ inr.
proof: Proof. apply (@exr_first _ O). Qed.
imports: Category.Lib Category.Theory.Category Category.Theory.Isomorphism Category.Structure.Cartesian Category.Structure.Initial Category.Construction.Opposite