old_contents: from rest_framework import serializers
  
  from ct.models import Response
  
  
  class ResponseSerializer(serializers.HyperlinkedModelSerializer):
      get_author_id = serializers.SerializerMethodField('author_id')
      get_lti_identity = serializers.SerializerMethodField('lti_identity')
      get_unitLesson_id = serializers.SerializerMethodField('unitLesson_id')
      get_unit_id = serializers.SerializerMethodField('unit_id')
  
      class Meta:
          model = Response
          fields = (
              'id',
              'get_author_id',
              'get_lti_identity',
              'text',
              'confidence',
              'selfeval',
              'status',
              'get_unitLesson_id',
              'get_unit_id'
          )
  
      def author_id(self, obj):
          """
          Returning author id.
          """
          return obj.author.id
  
      def lti_identity(self, obj):
          """
          Returning LTI user_id.
          """
          lti_user = obj.author.lti_auth.first()
          if lti_user:
              return lti_user.user_id
  
      def unitLesson_id(self, obj):
          """
          Returning UnitLesson id.
          """
          return obj.unitLesson.id
  
      def unit_id(self, obj):
          """
          Returning Unit id.
          """
          return obj.unitLesson.unit.id
  
new_contents: from rest_framework import serializers
  
  from ct.models import Response
  
  
  class ResponseSerializer(serializers.HyperlinkedModelSerializer):
      author_id = serializers.SerializerMethodField()
      lti_identity = serializers.SerializerMethodField()
      unitLesson_id = serializers.SerializerMethodField()
      unit_id = serializers.SerializerMethodField()
  
      class Meta:
          model = Response
          fields = (
              'id',
              'author_id',
              'lti_identity',
              'text',
              'confidence',
              'selfeval',
              'status',
              'unitLesson_id',
              'unit_id',
          )
  
      def get_author_id(self, obj):
          """
          Returning author id.
          """
          return obj.author.id
  
      def get_lti_identity(self, obj):
          """
          Returning LTI user_id.
          """
          lti_user = obj.author.lti_auth.first()
          if lti_user:
              return lti_user.user_id
  
      def get_unitLesson_id(self, obj):
          """
          Returning UnitLesson id.
          """
          return obj.unitLesson.id
  
      def get_unit_id(self, obj):
          """
          Returning Unit id.
          """
          return obj.unitLesson.unit.id
  
subject: fix fields naming