/**
  * Display a listing of the resource.
  *
  * @return Response
  */
 public function instrument($id)
 {
     $courses = Course::ofInstrument($id)->orderBy('day')->with('manager', 'users', 'instrument', 'article', 'documents')->paginate(20);
     $instrument = true;
     return view('admin.courses.index', compact('courses', 'instrument'));
 }