text: from django.contrib.auth.models import User, Group
  
  from rest_framework.serializers import ModelSerializer, HyperlinkedModelSerializer
  
  from bootcamp.authentication.models import Profile
  from bootcamp.activities.models import Activity, Notification
  from bootcamp.feeds.models import Feed
  from bootcamp.articles.models import Article, ArticleComment
  from bootcamp.messenger.models import Message
  
  
  class UserSerializer(HyperlinkedModelSerializer):
      class Meta:
          model = User
          fields = ('url', 'username', 'email', 'groups')
  
  
  class GroupSerializer(HyperlinkedModelSerializer):
      class Meta:
          model = Group
          fields = ('url', 'name')
  
  
  class ActivitySerializer(HyperlinkedModelSerializer):
      class Meta:
          model = Activity
          fields = ('user', 'activity_type', 'date', 'feed', 'question', 'answer')
  
  
  class FeedSerializer(HyperlinkedModelSerializer):
      class Meta:
          model = Feed
          fields = ('user', 'date', 'parent', 'likes', 'comments')
  
  
  class NotificationSerializer(HyperlinkedModelSerializer):
      class Meta:
          model = Notification
          fields = ('from_user', 'to_user', 'date', 'feed', 'question', 'answer',
                    'article', 'notification_type', 'is_read')
  
  
  class ArticleSerializer(HyperlinkedModelSerializer):
      class Meta:
          model = Article
          # TODO: 'tags' is instance of TaggableManager, adding it causes
          # Object of type '_TaggableManager' is not JSON serializable
          fields = ('title', 'slug', 'content', 'status', 'create_user',
                    'create_date', 'update_date', 'update_user')
  
  
  class ArticleCommentSerializer(HyperlinkedModelSerializer):
      class Meta:
          model = ArticleComment
          fields = ('article', 'comment', 'date', 'user')
  
  
  class MessageSerializer(HyperlinkedModelSerializer):
      class Meta:
          model = Message
          fields = ('user', 'message', 'date', 'conversation', 'from_user',
                    'is_read')