nested_serializer.py

serializers.py

class ItemSerializer(serializers.ModelSerializer):
    class Meta:
        model = Item
        fields = (
            'field1',
            'field2'
        )


class CategorySerializer(serializers.ModelSerializer):
    items = ItemSerializer(many=True, read_only=True)
    
    class Meta:
        model = Category
        fields = ('field1', 'items', 'field2')