previous_article = all_article[previous_index]
next_article = all_article[next_index]

这两句上哪去了

def get_detail_page(request, article_id):
    all_article = Article.objects.all()
    curr_article = None
    previous_article = None
    next_article = None
    for index, article in enumerate(all_article):
        if index == 0:
            previous_index = 0
            next_index = index + 1
        elif index == len(all_article) - 1:
            previous_index = index - 1
            next_index = index
        else:
            previous_index = index - 1
            next_index = index + 1
        previous_article = all_article[previous_index]
        next_article = all_article[next_index]
        if article.article_id == article_id:
            curr_article = article
            break
    section_list = curr_article.content.split('\n')
    return render(request, 'blog/detail.html', {
        'curr_article': curr_article,
        'section_list': section_list,
        'previous_article': previous_article,
        'next_article': next_article
    })

我是这样的