old_contents: from rest_framework import serializers
  
  from abacus_edu.models import Video
  
  
  class VideoModelSerializer(serializers.ModelSerializer):
      class Meta:
          model = Video
          fields = ('id', 'title', 'writer', 'youtube_id', 'youtube_original_url',
                    'youtube_thumbnail_image_url', 'youtube_embed_url', 'is_recommended', 'description',)
  
new_contents: from rest_framework import serializers
  
  from abacus_edu.models import Video
  
  
  class VideoModelSerializer(serializers.ModelSerializer):
      class Meta:
          model = Video
          fields = ('id', 'category', 'title', 'writer', 'youtube_id', 'youtube_original_url',
                    'youtube_thumbnail_image_url', 'youtube_embed_url', 'is_recommended', 'description',)
  
subject: update VideoModelSerializer