Get a suitable time string
        ("ss", "mm:ss", "hh:mm:ss"),
        according to the maximum time.

        :param int value: the time value
        :rtype: string

def _time_string(self, value):
        """
        Get a suitable time string
        ("ss", "mm:ss", "hh:mm:ss"),
        according to the maximum time.

        :param int value: the time value
        :rtype: string
        """
        if self.max_time < 60:
            return "%02d" % (value)
        elif self.max_time < 3600:
            mm = value // 60
            ss = value - mm * 60
            return "%02d:%02d" % (mm, ss)
        hh = value // 3600
        mm = (value - hh * 3600) // 60
        ss = (value - hh * 3600 - mm * 60)
        return "%02d:%02d:%02d" % (hh, mm, ss)