Django DRF外国键序列化程序-如何只返回最新的对象？

# models.py
from django.db import models

class Post(models.Model):
    title = models.CharField(max_length=100)
    content = models.TextField()

class Comment(models.Model):
    post = models.ForeignKey(Post, related_name='comments', on_delete=models.CASCADE)
    content = models.TextField()
    created_at = models.DateTimeField(auto_now_add=True)

# serializers.py
from rest_framework import serializers
from .models import Post, Comment

class LatestCommentSerializer(serializers.ModelSerializer):
    class Meta:
        model = Comment
        fields = ['content', 'created_at']

class PostSerializer(serializers.ModelSerializer):
    latest_comment = serializers.SerializerMethodField()

    class Meta:
        model = Post
        fields = ['title', 'content', 'latest_comment']

    def get_latest_comment(self, obj):
        latest_comment = obj.comments.order_by('-created_at').first()
        return LatestCommentSerializer(latest_comment).data if latest_comment else None