∀ {C : Type u_1} {D : Type u_2} [inst : CategoryTheory.Category.{v_1, u_1} C]
  [inst_1 : CategoryTheory.Category.{v_2, u_2} D] (L : CategoryTheory.Functor C D) {H : Type u_3}
  [inst_2 : CategoryTheory.Category.{v_3, u_3} H] (F : CategoryTheory.Functor C H)
  [inst_3 : L.HasPointwiseLeftKanExtension F] (X : D) (f : CategoryTheory.CostructuredArrow L X),
  CategoryTheory.CategoryStruct.comp ((L.leftKanExtensionUnit F).app f.left)
      (CategoryTheory.CategoryStruct.comp ((L.leftKanExtension F).map f.hom)
        (L.leftKanExtensionObjIsoColimit F X).hom) =
    CategoryTheory.Limits.colimit.ι ((CategoryTheory.CostructuredArrow.proj L X).comp F) f