∀ {C : Type u_1} [inst : CategoryTheory.Category.{v_1, u_1} C] {W : CategoryTheory.MorphismProperty C}
  [inst_1 : W.HasLeftCalculusOfFractions] {X Y : C} (f : W.LeftFraction X Y),
  CategoryTheory.MorphismProperty.LeftFraction.Localization.homMk f =
    CategoryTheory.MorphismProperty.LeftFraction.Localization.Hom.mk f