∀ {C : Type u_1} [inst : CategoryTheory.Category.{v_1, u_1} C] [inst_1 : CategoryTheory.Preadditive C]
  {S₁ S₂ : CategoryTheory.ShortComplex C} {φ φ' : S₁ ⟶ S₂} (h₁ : S₁.LeftHomologyData) (h₂ : S₂.LeftHomologyData),
  CategoryTheory.ShortComplex.leftHomologyMap' (φ + φ') h₁ h₂ =
    CategoryTheory.ShortComplex.leftHomologyMap' φ h₁ h₂ + CategoryTheory.ShortComplex.leftHomologyMap' φ' h₁ h₂