Returns data as JSON
        
        Returns:
          json_data (str): JSON representation of data, as created in make_data

def json_data(self):
        """Returns data as JSON
        
        Returns:
          json_data (str): JSON representation of data, as created in make_data
        """
        def stringify_keys(d):
            if not isinstance(d, dict):
                return d
            return dict((str(k), stringify_keys(v)) for k, v in d.items())
        data = self.make_data()
        json_data = json.dumps(stringify_keys(data))
        return json_data