old_contents: from models import ChannelMetadata
  from rest_framework import serializers
  
  
  class ChannelMetadataSerializer(serializers.HyperlinkedModelSerializer):
  
      contentmetadatas = serializers.HyperlinkedIdentityField(
          lookup_field='channel_id', view_name='contentmetadata-list', lookup_url_kwarg='channelmetadata_channel_id')
  
      class Meta:
          model = ChannelMetadata
          fields = ('url', 'channel_id', 'name', 'description', 'author', 'theme', 'subscribed', 'contentmetadatas')
          extra_kwargs = {
              'url': {'lookup_field': 'channel_id', 'view_name': 'channelmetadata-detail'}
          }
  
new_contents: from models import ChannelMetadata, ContentMetadata
  from rest_framework import serializers
  
  
  class ChannelMetadataSerializer(serializers.HyperlinkedModelSerializer):
  
      contentmetadatas = serializers.HyperlinkedIdentityField(
          lookup_field='channel_id', view_name='contentmetadata-list', lookup_url_kwarg='channelmetadata_channel_id')
  
      class Meta:
          model = ChannelMetadata
          fields = ('url', 'channel_id', 'name', 'description', 'author', 'theme', 'subscribed', 'contentmetadatas')
          extra_kwargs = {
              'url': {'lookup_field': 'channel_id', 'view_name': 'channelmetadata-detail'}
          }
  
  
  class ContentMetadataSerializer(serializers.ModelSerializer):
  
      class Meta:
          model = ContentMetadata
          depth = 1
          fields = (
              'content_id', 'title', 'description', 'kind', 'slug', 'total_file_size', 'available', 'license', 'parent', 'prerequisite', 'is_related'
          )
  
subject: add basic serializer for contentmetadata