∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] {X Y : C} (f : X ⟶ Y)
  [inst_1 : HomotopicalAlgebra.CategoryWithWeakEquivalences C],
  HomotopicalAlgebra.WeakEquivalence f ↔ HomotopicalAlgebra.weakEquivalences C f