∀ {C : Type u_3} {D : Type u_4} {H : Type u_6} [inst : CategoryTheory.Category.{u_1, u_3} C]
  [inst_1 : CategoryTheory.Category.{u_2, u_4} D] [inst_2 : CategoryTheory.Category.{u_5, u_6} H]
  {L : CategoryTheory.Functor C D} {F : CategoryTheory.Functor C H} (E : L.RightExtension F) {Y Y' : D} (e : Y ≅ Y')
  (j : CategoryTheory.StructuredArrow Y' L),
  (CategoryTheory.Limits.Cone.whisker (CategoryTheory.StructuredArrow.mapIso e.symm).functor (E.coneAt Y)).π.app j =
    CategoryTheory.CategoryStruct.comp (E.left.mapIso e).hom ((E.coneAt Y').π.app j)