∀ {B : Type u_3} [inst : CategoryTheory.Bicategory B] {a b : B} (u : b ⟶ a)
  (motive :
    (∃ (x : CategoryTheory.Bicategory.HasLeftKanLift u (CategoryTheory.CategoryStruct.id a)),
        CategoryTheory.Bicategory.LanLift.CommuteWith u (CategoryTheory.CategoryStruct.id a) u) →
      Prop)
  (x :
    ∃ (x : CategoryTheory.Bicategory.HasLeftKanLift u (CategoryTheory.CategoryStruct.id a)),
      CategoryTheory.Bicategory.LanLift.CommuteWith u (CategoryTheory.CategoryStruct.id a) u),
  (∀ (h : CategoryTheory.Bicategory.HasLeftKanLift u (CategoryTheory.CategoryStruct.id a))
      (h' : CategoryTheory.Bicategory.LanLift.CommuteWith u (CategoryTheory.CategoryStruct.id a) u), motive ⋯) →
    motive x