old_contents: import json
  
  class JSONSerialized(object):
      @classmethod
      def loads(cls, string):
          return cls(json.loads(string))
  
      def dumps(self):
          return json.dumps(self)
  
  class DataSet(dict, JSONSerialized):
      pass
  
  class Indices(list, JSONSerialized):
      pass
  
  class Index(dict, JSONSerialized):
      pass
  
  class Keys(list, JSONSerialized):
      pass
  
  class Values(list, JSONSerialized):
      pass
  
new_contents: from django.utils import simplejson as json
  
  class JSONSerialized(object):
      @classmethod
      def loads(cls, string):
          return cls(json.loads(string))
  
      def dumps(self):
          return json.dumps(self)
  
  class DataSet(dict, JSONSerialized):
      pass
  
  class Indices(list, JSONSerialized):
      pass
  
  class Index(dict, JSONSerialized):
      pass
  
  class Keys(list, JSONSerialized):
      pass
  
  class Values(list, JSONSerialized):
      pass
  
subject: use django.utils.simplejson instead of json (everywhere)