old_contents: from rest_framework import serializers, viewsets
  
  from cyder.api.v1.endpoints.api import CommonAPINestedAVSerializer
  from cyder.core.system.models import System, SystemAV
  
  
  class SystemAVSerializer(serializers.ModelSerializer):
      id = serializers.Field(source='id')
      entity = serializers.HyperlinkedRelatedField(
          source="entity", view_name='api-core-system-detail')
      attribute = serializers.SlugRelatedField(slug_field='name')
  
      class Meta:
          model = SystemAV
  
  
  class SystemAVViewSet(viewsets.ModelViewSet):
      model = SystemAV
      queryset = SystemAV.objects.all()
      serializer_class = SystemAVSerializer
  
  
  class SystemNestedAVSerializer(CommonAPINestedAVSerializer):
      id = serializers.HyperlinkedIdentityField(
          view_name='api-core-system_attributes-detail')
      attribute = serializers.SlugRelatedField(slug_field='name')
  
      class Meta:
          model = SystemAV
          fields = ['id', 'attribute', 'value']
  
  
  class SystemSerializer(serializers.ModelSerializer):
      systemav_set = SystemNestedAVSerializer(many=True)
  
      class Meta:
          model = System
  
  
  class SystemViewSet(viewsets.ModelViewSet):
      queryset = System.objects.all()
      serializer_class = SystemSerializer
      avmodel = SystemAV
  
new_contents: from rest_framework import serializers, viewsets
  
  from cyder.api.v1.endpoints.api import CommonAPINestedAVSerializer
  from cyder.core.system.models import System, SystemAV
  
  
  class SystemAVSerializer(serializers.ModelSerializer):
      id = serializers.Field(source='id')
      entity = serializers.HyperlinkedRelatedField(
          view_name='api-core-system-detail')
      attribute = serializers.SlugRelatedField(slug_field='name')
  
      class Meta:
          model = SystemAV
  
  
  class SystemAVViewSet(viewsets.ModelViewSet):
      model = SystemAV
      queryset = SystemAV.objects.all()
      serializer_class = SystemAVSerializer
  
  
  class SystemNestedAVSerializer(CommonAPINestedAVSerializer):
      id = serializers.HyperlinkedIdentityField(
          view_name='api-core-system_attributes-detail')
      attribute = serializers.SlugRelatedField(slug_field='name')
  
      class Meta:
          model = SystemAV
          fields = ['id', 'attribute', 'value']
  
  
  class SystemSerializer(serializers.ModelSerializer):
      systemav_set = SystemNestedAVSerializer(many=True)
  
      class Meta:
          model = System
  
  
  class SystemViewSet(viewsets.ModelViewSet):
      queryset = System.objects.all()
      serializer_class = SystemSerializer
      avmodel = SystemAV
  
subject: Remove extraneous argument