问AttributeError: QuerySet对象没有属性“related_stocks”

EN

class Topic(models.Model):
    title = models.CharField(max_length=50)
    related_stocks = models.ManyToManyField(Stock)
    slug = models.SlugField(max_length=200, blank=True)
    created = models.DateField(auto_now_add=True,
                           db_index=True)
    def __str__(self):
    return self.title

    def save(self, *args, **kwargs):
        if not self.slug:
            self.slug = slugify(self.title)
            super(Topic, self).save(*args, **kwargs)

    def get_absolute_url(self):
        return reverse('comments:topic_detail', args=[self.id, self.slug])

def topic_detail(request, id, slug):
    topic = Topic.objects.all().filter(id=id, slug=slug)
    related_stocks = topic.related_stocks
    return render(request,
                  'comments/comment/topic-detail.html',
                  {'section': 'topics',
                   'topic': topic,
                   'related_stocks': related_stocks})

{% extends "base.html" %}

{% block title %}{{ topic.title }}{% endblock %}

{% block content %}
    <h1>Stocks associated with {{ topic.title }}.</h1>
    {% for related_stock in related_stocks %}
    <ul>
        <a href="{{ related_stock.get_absolute_url }}">
            {{ related_stock.ticker }}
        </a>
    </ul>
    {% endfor %}
{% endblock %}