'Updates a local copy of attributes values'

def _update_tracked_data(self):

    if self.id:
        data = {}
        for f in self._meta.fields:
            try:
                data[f.column] = self.__get_field_value(f)
            except AttributeError as e:
                logging.exception(six.text_type(e))
        self.__data = data
    else:
        self.__data = UNSAVED
