∀ {C : Type u_2} [inst : CategoryTheory.Category.{u_1, u_2} C] {X Y : Cᵒᵖ} {f : X ⟶ Y}
  [inst_1 : CategoryTheory.Limits.HasPullback f.unop f.unop],
  CategoryTheory.CategoryStruct.comp f.unop.op (CategoryTheory.Limits.pullback.fst f.unop f.unop).op =
    CategoryTheory.CategoryStruct.comp f.unop.op (CategoryTheory.Limits.pullback.snd f.unop f.unop).op