{C : Type u} →
  [inst : CategoryTheory.Category.{v, u} C] →
    [inst_1 : CategoryTheory.Abelian C] →
      [inst_2 : CategoryTheory.HasExt C] →
        {Y Z : C} →
          {n : ℕ} →
            CategoryTheory.Abelian.Ext Y Z n →
              (R : Type t) →
                [inst_3 : CommRing R] →
                  [inst_4 : CategoryTheory.Linear R C] →
                    (X : C) →
                      {a b : ℕ} → a + n = b → CategoryTheory.Abelian.Ext X Y a →ₗ[R] CategoryTheory.Abelian.Ext X Z b