old_contents: from rest_framework import serializers
  from dwitter.models import Dweet, Comment
  from django.contrib.auth.models import User
  
  class UserSerializer(serializers.ModelSerializer):
    class Meta:
      model = User
      fields = ('pk', 'username')
  
  class CommentSerializer(serializers.ModelSerializer):
    author = serializers.ReadOnlyField(source='author.username') 
    posted = serializers.ReadOnlyField()
    class Meta:
      model = Comment
      fields = ('text', 'posted', 'reply_to', 'author')
  
  class DweetSerializer(serializers.ModelSerializer):
    latest_comments = serializers.SerializerMethodField()
    reply_to = serializers.PrimaryKeyRelatedField(queryset=Dweet.objects.all())
  
    class Meta:
      model = Dweet
      fields = ('pk', 'code', 'posted', 'author', 'likes','reply_to', 'latest_comments')
  
    def get_latest_comments(self, obj):
      cmnts = obj.comments.all().order_by('-posted')
      return CommentSerializer(cmnts[:3], many=True).data
      
  
  
  
  
  
new_contents: from rest_framework import serializers
  from dwitter.models import Dweet, Comment
  from django.contrib.auth.models import User
  
  class UserSerializer(serializers.ModelSerializer):
    class Meta:
      model = User
      fields = ('pk', 'username')
  
  class CommentSerializer(serializers.ModelSerializer):
    author = serializers.ReadOnlyField(source='author.username') 
    posted = serializers.ReadOnlyField()
    class Meta:
      model = Comment
      fields = ('text', 'posted', 'reply_to', 'author')
  
  class DweetSerializer(serializers.ModelSerializer):
    latest_comments = serializers.SerializerMethodField()
    reply_to = serializers.PrimaryKeyRelatedField(queryset=Dweet.objects.all())
  
    class Meta:
      model = Dweet
      fields = ('pk', 'code', 'posted', 'author', 'likes','reply_to', 'latest_comments')
  
    def get_latest_comments(self, obj):
      cmnts = obj.comments.all().order_by('-posted')
      return CommentSerializer(cmnts[:3], many=True).data
  
subject: Remove whitespace at end of file