∀ {C : Type u_1} [inst : CategoryTheory.Category.{v_1, u_1} C] {W : CategoryTheory.MorphismProperty C}
  [inst_1 : W.HasLeftCalculusOfFractions] {X Y : C} (s : X ⟶ Y) (hs : W s)
  {Z : CategoryTheory.MorphismProperty.LeftFraction.Localization W}
  (h : (CategoryTheory.MorphismProperty.LeftFraction.Localization.Q W).obj X ⟶ Z),
  CategoryTheory.CategoryStruct.comp ((CategoryTheory.MorphismProperty.LeftFraction.Localization.Q W).map s)
      (CategoryTheory.CategoryStruct.comp (CategoryTheory.MorphismProperty.LeftFraction.Localization.Qinv s hs) h) =
    h