∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] [inst_1 : CategoryTheory.Abelian C]
  [inst_2 : HasDerivedCategory C] {S : CategoryTheory.ShortComplex C} (hS : S.ShortExact),
  hS.singleTriangle.obj₃ = (DerivedCategory.singleFunctor C 0).obj S.X₃