∀ {C : Type u_1} [inst : CategoryTheory.Category.{v_1, u_1} C] {W : CategoryTheory.MorphismProperty C} {X Y : C}
  {z₁ z₂ : W.LeftFraction₂ X Y},
  CategoryTheory.MorphismProperty.LeftFraction₂Rel z₁ z₂ → CategoryTheory.MorphismProperty.LeftFractionRel z₁.fst z₂.fst