更新表单时，Formset显示无效

Question

任何人都可以帮助我，为什么我的表单集在尝试更新表单时显示为无效。创建表单时，它可以完美地工作。普通表单正在编辑，但表单集不是。

`def content_edit_view（请求，ID）： 路线= get_object_or_404（课程，id = id） LectureFormset = modelformset_factory（讲座，字段=（'lecture_title'，'lecture_content'，'youtube_url'），extra = 0）

if course.user != request.user:
    raise Http404()

if request.method == 'POST':
    content_edit_form = ContentEditForm(request.POST or None, request.FILES or None, instance=course)
    formset = LectureFormset(request.POST or None, request.FILES or None)

    if content_edit_form.is_valid(): 
        content_edit_form.save()
        data = Lecture.objects.filter(course=course)

        # give index of the item for a formset item strting form 0 and (f)the item itself 
        if formset.is_valid():
            for index, f in enumerate(formset):
                if f.cleaned_data:
                    if f.cleaned_data['id'] is None:
                        video = Lecture(course=course, lecture_title=f.cleaned_data.get('lecture_title'), lecture_content=f.cleaned_data.get('lecture_content'), youtube_url=f.cleaned_data.get('youtube_url'))
                        video.save()
                    else:
                        video = Lecture(course=course, lecture_title=f.cleaned_data.get('lecture_title'), lecture_content=f.cleaned_data.get('lecture_content'), youtube_url=f.cleaned_data.get('youtube_url'))              
                        d = Lecture.objects.get(id=data[index].id) #get slide id which was uploaded
                        d.lecture_title = video.lecture_title # changing the database tiitle with new title
                        d.lecture_content = video.lecture_content #changing the database content with new content
                        d.youtube_url = video.youtube_url # changing the database content with new content
                        d.save()

            return redirect('teacher-profile')

        else:
            print('formset is invalid')

    else:
        print("form is invalid")

else:
    content_edit_form = ContentEditForm(instance=course)
    formset = LectureFormset(queryset=Lecture.objects.filter(course=course))

context = {
    'contentForm': content_edit_form,
    'course': course,
    'formset': formset,
}


return render(request, 'apps/contentEdit.html', context)`