∀ {C : Type u₁} [inst : CategoryTheory.Category.{v₁, u₁} C] [inst_1 : CategoryTheory.ChosenPullbacks C] {X : C}
  (Y : CategoryTheory.Over X),
  CategoryTheory.CategoryStruct.comp (CategoryTheory.MonoidalCategoryStruct.rightUnitor Y).inv.left
      (CategoryTheory.ChosenPullbacksAlong.snd Y.hom (CategoryTheory.CategoryStruct.id X)) =
    Y.hom