∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] [inst_1 : CategoryTheory.Limits.HasZeroMorphisms C] (X Y : C)
  [inst_2 : CategoryTheory.Limits.HasBinaryCoproduct X Y] {Z : C} (h : Y ⟶ Z),
  CategoryTheory.CategoryStruct.comp CategoryTheory.Limits.coprod.inr
      (CategoryTheory.CategoryStruct.comp (CategoryTheory.Limits.coprod.snd X Y) h) =
    h