'Return self.__field_name or \'site\' or \'sites\'.'

def _get_field_name(self):

    if (not self.__field_name):
        try:
            self.model._meta.get_field('site')
        except FieldDoesNotExist:
            self.__field_name = 'sites'
        else:
            self.__field_name = 'site'
    return self.__field_name
