old_contents: from rest_framework import serializers
  from drf_compound_fields import fields as compound_fields
  
  
  class UserSignupSerializer(serializers.Serializer):
      first_name = serializers.CharField(max_length=200)
      last_name = serializers.CharField(max_length=200)
      email = serializers.EmailField(max_length=200)
      password = serializers.CharField(max_length=200)
      secret_key = serializers.CharField(max_length=100)
      course_id = serializers.CharField(max_length=200, required=False)
      full_name = serializers.SerializerMethodField('get_full_name')
  
      def get_full_name(self, obj):
          return u"{0} {1}".format(obj.get('first_name'), obj.get('last_name'))
  
new_contents: from rest_framework import serializers
  
  
  class UserSignupSerializer(serializers.Serializer):
      first_name = serializers.CharField(max_length=200)
      last_name = serializers.CharField(max_length=200)
      email = serializers.EmailField(max_length=200)
      password = serializers.CharField(max_length=200)
      secret_key = serializers.CharField(max_length=100)
      course_id = serializers.CharField(max_length=200, required=False)
      full_name = serializers.SerializerMethodField('get_full_name')
  
      def get_full_name(self, obj):
          return u"{0} {1}".format(obj.get('first_name'), obj.get('last_name'))
  
subject: remove import from package that doesn't exist anymore