public function store(Request $request, $lecture_id)
 {
     $this->validate($request, ['title' => 'required', 'description' => 'required']);
     $lecture = Lecture::find($lecture_id);
     //Log::info('$subject_id: '.$lecture->title);
     $subject = new Subject();
     $subject->title = $request->title;
     $subject->description = $request->description;
     $subject->lecture()->associate($lecture);
     $subject->save();
     return redirect('/lectures/' . $lecture_id . '/subjects');
 }