∀ {J : Type u₁} [inst : CategoryTheory.Category.{v₁, u₁} J] {C : Type u₃} [inst_1 : CategoryTheory.Category.{v₃, u₃} C]
  {F : CategoryTheory.Functor J C} (X : CategoryTheory.Limits.Cone F),
  (CategoryTheory.Limits.Cones.postcomposeId.hom.app X).hom = CategoryTheory.CategoryStruct.id X.pt