∀ {C : Type u_1} {H : Type u_3} {D : Type u_6} [inst : CategoryTheory.Category.{u_4, u_1} C]
  [inst_1 : CategoryTheory.Category.{u_2, u_3} H] [inst_2 : CategoryTheory.Category.{u_5, u_6} D]
  (F' : CategoryTheory.Functor D H) {L : CategoryTheory.Functor C D} {F : CategoryTheory.Functor C H}
  (α : F ⟶ L.comp F') [inst_3 : F'.IsLeftKanExtension α] (G : CategoryTheory.Functor D H) (β : F' ⟶ G),
  CategoryTheory.CategoryStruct.comp α
      (L.whiskerLeft
        ((fun β => F'.descOfIsLeftKanExtension α G β)
          ((fun β => CategoryTheory.CategoryStruct.comp α (L.whiskerLeft β)) β))) =
    CategoryTheory.CategoryStruct.comp α (L.whiskerLeft β)