∀ {A : Type u₁} [inst : CategoryTheory.Category.{v₁, u₁} A]
  (L : CategoryTheory.Functor A (CategoryTheory.Discrete PUnit.{u_1 + 1}))
  (R : CategoryTheory.Functor (CategoryTheory.Discrete PUnit.{u_2 + 1}) (CategoryTheory.Discrete PUnit.{u_1 + 1}))
  (X : CategoryTheory.Comma L R),
  ((CategoryTheory.Comma.toPUnitIdEquiv L R).unitIso.hom.app X).left = CategoryTheory.CategoryStruct.id X.left