在以下情况下如何在django中使用annotate函数？

from django.db import models
from django.db.models import Count

class Post(models.Model):
    title = models.CharField(max_length=200)
    content = models.TextField()

class Comment(models.Model):
    post = models.ForeignKey(Post, related_name='comments', on_delete=models.CASCADE)
    text = models.TextField()

# 使用annotate()函数获取每个帖子的评论数量
posts_with_comment_count = Post.objects.annotate(comment_count=Count('comments'))

for post in posts_with_comment_count:
    print(f"Post: {post.title}, Comment Count: {post.comment_count}")

from django.db.models import Case, When, Value

# 条件注解示例：如果帖子标题包含'重要'，则标记为'High Priority'
posts_with_priority = Post.objects.annotate(
    priority=Case(
        When(title__icontains='重要', then=Value('High Priority')),
        default=Value('Normal'),
        output_field=models.CharField()
    )
)