∀ {C : Type u_2} [inst : CategoryTheory.Category.{u_1, u_2} C] [inst_1 : CategoryTheory.Preadditive C]
  {S₁ S₂ : CategoryTheory.ShortComplex C} (H₁ : S₁.LeftHomologyData) (H₂ : S₂.LeftHomologyData) (h₁ : S₁.X₂ ⟶ S₂.X₁),
  CategoryTheory.CategoryStruct.comp H₁.π 0 =
    CategoryTheory.CategoryStruct.comp
      (H₂.liftK (CategoryTheory.CategoryStruct.comp H₁.i (CategoryTheory.CategoryStruct.comp h₁ S₂.f)) ⋯) H₂.π