∀ {C : Type u_1} [inst : CategoryTheory.Category.{v_1, u_1} C] [inst_1 : CategoryTheory.Preadditive C]
  [inst_2 : CategoryTheory.Limits.HasBinaryBiproducts C] [inst_3 : CategoryTheory.Limits.HasZeroObject C]
  (X : HomotopyCategory C (ComplexShape.up ℤ)),
  CategoryTheory.Pretriangulated.contractibleTriangle X ∈ HomotopyCategory.Pretriangulated.distinguishedTriangles C