∀ {J : Type u_1} {C : Type u_2} [inst : CategoryTheory.Category.{v_1, u_1} J]
  [inst_1 : CategoryTheory.Category.{v_2, u_2} C] {D : CategoryTheory.Functor J C} (c : CategoryTheory.Limits.Cone D)
  (j : J) (k : CategoryTheory.Over j), (c.overPost j).π.app k = CategoryTheory.Over.homMk (c.π.app k.left) ⋯