∀ {C : Type u_2} [inst : CategoryTheory.Category.{u_1, u_2} C] (F : CategoryTheory.Functor Cᵒᵖ (Type u_1))
  (X : F.Elementsᵒᵖ),
  F.map
      (CategoryTheory.Iso.refl
          ((CategoryTheory.CategoryOfElements.fromCostructuredArrow F).obj
              (Opposite.op ((CategoryTheory.CategoryOfElements.toCostructuredArrow F).obj X))).fst).hom
      ((CategoryTheory.CategoryOfElements.fromCostructuredArrow F).obj
          (Opposite.op ((CategoryTheory.CategoryOfElements.toCostructuredArrow F).obj X))).snd =
    (Opposite.unop X).snd