∀ {C : Type u_2} {D : Type u_3} [inst : CategoryTheory.Category.{u_1, u_2} C]
  [inst_1 : CategoryTheory.Category.{u_1, u_3} D] (i : CategoryTheory.Functor D C)
  [inst_2 : CategoryTheory.Reflective i] (X : i.EssImageSubcategory),
  CategoryTheory.IsIso ((CategoryTheory.reflectorAdjunction i).unit.app X.obj)