old_contents: from django.contrib.auth.models import User, Group
  from rest_framework import serializers
  
  class UserSerializer(serializers.HyperlinkedModelSerializer):
      class Meta:
          model = User
          fields = ('url', 'username', 'email', 'groups')
  
  class GroupSerializer(serializers.HyperlinkedModelSerializer):
      class Meta:
          model = Group
          fields = ('url', 'name')
  
  from msg.models import Msg
  
  class MsgSerializer( serializers.ModelSerializer ):
      class Meta:
          model = Msg
          fields = ('source','destination','channel','signature','body')
  
  
  class MsgListSerializer( serializers.ModelSerializer ):
      class Meta:
          model = Msg
          fields = ( 'source','timestamp','destination','channel','signature','body')
  
  
  
new_contents: from django.contrib.auth.models import User, Group
  from rest_framework import serializers
  
  class UserSerializer(serializers.HyperlinkedModelSerializer):
      class Meta:
          model = User
          fields = ('url', 'username', 'email', 'groups')
  
  class GroupSerializer(serializers.HyperlinkedModelSerializer):
      class Meta:
          model = Group
          fields = ('url', 'name')
  
  from msg.models import Msg
  
  class MsgSerializer( serializers.ModelSerializer ):
      class Meta:
          model = Msg
          fields = ('message_id','timestamp','source','destination','channel','signature','body')
  
  
  class MsgListSerializer( serializers.ModelSerializer ):
      class Meta:
          model = Msg
          fields = ( 'source','timestamp','destination','channel','signature','body')
  
  
  
subject: Update serializers.py