∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] [inst_1 : CategoryTheory.Preadditive C]
  [inst_2 : CategoryTheory.Limits.HasBinaryBiproducts C] {X₁ X₂ : C} (r : X₂ ⟶ X₁),
  (CategoryTheory.Biprod.unipotentLower r).inv =
    CategoryTheory.Biprod.ofComponents (CategoryTheory.CategoryStruct.id X₁) 0 (-r)
      (CategoryTheory.CategoryStruct.id X₂)