∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] (X : CategoryTheory.SimplicialObject C) (n : ℕ)
  [inst_1 :
    ∀ (F : CategoryTheory.Functor (SimplexCategory.Truncated n)ᵒᵖ C),
      (SimplexCategory.Truncated.inclusion n).op.HasRightKanExtension F]
  [X.IsCoskeletal n], CategoryTheory.IsIso ((CategoryTheory.SimplicialObject.coskAdj n).unit.app X)