每當(dāng)我創(chuàng)建以后可以重用的DRY函數(shù)，然后在模型中使用它們時(shí)，我都會得到循環(huán)引用。例如：我有以下型號：from social.services import get_top_viewed_postsclass Post(models.Model):      customer = models.ForeignKey(Customer, on_delete=models.CASCADE)    title = models.CharField('Post Title', max_length=255) class ActivityUpdateEmail(models.Model):    sent = models.BooleanField(default=False)    created_at = models.DateTimeField(auto_now_add=True)    updated_at = models.DateTimeField(auto_now = True)    def send(self):                posts = get_top_viewed_posts()我查看次數(shù)最多的帖子功能是另一個(gè)名為services.py的文件，因此我可以在其他地方訪問它。看起來像：from social.models import Postdef get_top_viewed_posts():    posts = Post.objects.filter(        pk__in=popular_posts_ids,        ).order_by(                '-created_at'                )    return posts然后我得到錯誤：services.py", line 1, in <module>    from social.models import PostImportError: cannot import name 'Post'如果我將其更改為：交易= Action.objects.filter（content_type__pk = 35，created_at__gte = start_date，）.values_list（'object_id'，flat = True）popular_posts_ids = []popular_posts = Counter(transactions).most_common()[:result_amount]for dic in popular_posts:    popular_posts_ids.append(dic[0])class ActivityUpdateEmail(models.Model):    sent = models.BooleanField(default=False)    created_at = models.DateTimeField(auto_now_add=True)    updated_at = models.DateTimeField(auto_now = True)    def send(self):           posts = Post.objects.filter(              pk__in=popular_posts_ids,         ).order_by(            '-created_at'            )這沒問題。如何使用這種干燥的抽象功能方法，然后在模型中使用它們？