old_contents: from rest_framework import serializers
  from activities.models import Activity, Episode
  from clubs.models import Club
  from media.models import Buzz, BuzzView
  from niqati.models import Code, Category, Code_Collection, Code_Order
  
  class EpisodeSerializer(serializers.ModelSerializer):
      class Meta:
          model = Episode
          fields = ('pk', 'start_datetime', 'end_datetime')
  
  class ClubSerializer(serializers.ModelSerializer):
      class Meta:
          model = Club
          fields = ('pk', 'name', 'english_name', 'email', 'coordinator', 'gender', 'city')
  
  class ActivitySerializer(serializers.ModelSerializer):
      primary_club = ClubSerializer(read_only=True)
      secondary_clubs = ClubSerializer(many=True, read_only=True)
      episode_set = EpisodeSerializer(many=True, read_only=True)
      class Meta:
          model = Activity
          fields = ('pk', 'name', 'primary_club', 'secondary_clubs', 'public_description', 'episode_set', 'gender')
  
  class BuzzSerializer(serializers.ModelSerializer):
      class Meta:
          model = Buzz
          fields = ('pk', 'title', 'body', 'image', 'is_push')
  
  class BuzzViewSerializer(serializers.ModelSerializer):
      class Meta:
          model = BuzzView
          fields = ('pk', 'viewer', 'buzz', 'off_date')
  
  class NiqatiActivitySerializer(serializers.ModelSerializer):
      class Meta:
          model = Activity
          fields = ('name',)
  
  
  class NiqatiEpisodeSerializer(serializers.ModelSerializer):
      activity = NiqatiActivitySerializer(read_only=True)
      class Meta:
          model = Episode
          fields = ('activity',)
  
  class OrderSerializer(serializers.ModelSerializer):
      episode = NiqatiEpisodeSerializer(read_only=True)
      class Meta:
          model = Code_Order
          fields = ('episode',)
  
  class NiqatiCategorySerializer(serializers.ModelSerializer):
      class Meta:
          model = Category
          fields = ('ar_label',)
  
  class CollectionSerializer(serializers.ModelSerializer):
      parent_order = OrderSerializer(read_only=True)
      code_category = NiqatiCategorySerializer(read_only=True)
      class Meta:
          model = Code_Collection
          fields = ('code_category', 'parent_order')
  
  class CodeSerializer(serializers.ModelSerializer):
      collection = CollectionSerializer(read_only=True)
      class Meta:
          model = Code
          fields = ('pk', 'points', 'redeem_date', 'collection')
  
new_contents: from rest_framework import serializers
  from activities.models import Activity, Episode
  from activities.models import Category as ActivityCategory
  from clubs.models import Club
  from media.models import Buzz, BuzzView
  from niqati.models import Code, Category, Code_Collection, Code_Order
  
  class EpisodeSerializer(serializers.ModelSerializer):
      class Meta:
          model = Episode
          fields = ('pk', 'start_datetime', 'end_datetime')
  
  class ClubSerializer(serializers.ModelSerializer):
      class Meta:
          model = Club
          fields = ('pk', 'name', 'english_name', 'email', 'coordinator', 'gender', 'city')
  
  class ActivityCategorySerializer(serializers.ModelSerializer):
      class Meta:
          model = ActivityCategory
          fields = ('pk', 'ar_name')
  
  class ActivitySerializer(serializers.ModelSerializer):
      primary_club = ClubSerializer(read_only=True)
      category = ActivityCategorySerializer(read_only=True)
      secondary_clubs = ClubSerializer(many=True, read_only=True)
      episode_set = EpisodeSerializer(many=True, read_only=True)
      class Meta:
          model = Activity
          fields = ('pk', 'name', 'primary_club', 'secondary_clubs', 'public_description', 'episode_set', 'gender', 'category')
  
  class BuzzSerializer(serializers.ModelSerializer):
      class Meta:
          model = Buzz
          fields = ('pk', 'title', 'body', 'image', 'is_push')
  
  class BuzzViewSerializer(serializers.ModelSerializer):
      class Meta:
          model = BuzzView
          fields = ('pk', 'viewer', 'buzz', 'off_date')
  
  class NiqatiActivitySerializer(serializers.ModelSerializer):
      class Meta:
          model = Activity
          fields = ('name',)
  
  
  class NiqatiEpisodeSerializer(serializers.ModelSerializer):
      activity = NiqatiActivitySerializer(read_only=True)
      class Meta:
          model = Episode
          fields = ('activity',)
  
  class OrderSerializer(serializers.ModelSerializer):
      episode = NiqatiEpisodeSerializer(read_only=True)
      class Meta:
          model = Code_Order
          fields = ('episode',)
  
  class NiqatiCategorySerializer(serializers.ModelSerializer):
      class Meta:
          model = Category
          fields = ('ar_label',)
  
  class CollectionSerializer(serializers.ModelSerializer):
      parent_order = OrderSerializer(read_only=True)
      code_category = NiqatiCategorySerializer(read_only=True)
      class Meta:
          model = Code_Collection
          fields = ('code_category', 'parent_order')
  
  class CodeSerializer(serializers.ModelSerializer):
      collection = CollectionSerializer(read_only=True)
      class Meta:
          model = Code
          fields = ('pk', 'points', 'redeem_date', 'collection')
  
subject: Include Activity's Category in the API call.