@classmethod
def record_id(cls, event, stamp):
    """
        Return a string suitable for use as the document id.

        :param event: A event identifier
        :param stamp: Datetime for this event
        :type event: str
        :type stamp: datetime.datetime

        """
    period = cls._period(stamp)
    info = {'event': event, 'year': period.year, 'month': period.month,
        'day': period.day, 'hour': period.hour, 'minute': period.minute}
    return cls.config_id_format % info
