∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] {X Y : C} {f g : X ⟶ Y} {Z : C} {π : Y ⟶ Z}
  (self : CategoryTheory.IsSplitCoequalizer f g π) {Z_1 : C} (h : Z ⟶ Z_1),
  CategoryTheory.CategoryStruct.comp f (CategoryTheory.CategoryStruct.comp π h) =
    CategoryTheory.CategoryStruct.comp g (CategoryTheory.CategoryStruct.comp π h)