∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] [inst_1 : CategoryTheory.Limits.HasZeroMorphisms C]
  [inst_2 : CategoryTheory.Limits.HasBinaryBiproducts C] (X Y : C) (f g h k : X ⟶ Y),
  CategoryTheory.SemiadditiveOfBinaryBiproducts.leftAdd X Y
      (CategoryTheory.SemiadditiveOfBinaryBiproducts.rightAdd X Y f g)
      (CategoryTheory.SemiadditiveOfBinaryBiproducts.rightAdd X Y h k) =
    CategoryTheory.SemiadditiveOfBinaryBiproducts.rightAdd X Y
      (CategoryTheory.SemiadditiveOfBinaryBiproducts.leftAdd X Y f h)
      (CategoryTheory.SemiadditiveOfBinaryBiproducts.leftAdd X Y g k)