How to use the execo.time_utils.get_seconds function in execo

def make_reservation(self):
        """Perform a reservation of the required number of nodes."""

        logger.info('Performing reservation')
        now = int(time.time() + timedelta_to_seconds(datetime.timedelta(minutes=1)))
        starttime = now
        endtime = int(starttime + timedelta_to_seconds(datetime.timedelta(days=3,
                                                                 minutes=1)))
        startdate, n_nodes = self._get_nodes(starttime, endtime)

        search_time = 3 * 24 * 60 * 60  # 3 days
        walltime_seconds = get_seconds(self.options.walltime)

        iteration = 0
        while not n_nodes:
            iteration += 1
            logger.info('Not enough nodes found between %s and %s, ' +
                        'increasing time window',
                        format_date(starttime), format_date(endtime))
            starttime = max(now, now + iteration * search_time - walltime_seconds)
            endtime = int(now + (iteration + 1) * search_time)

            startdate, n_nodes = self._get_nodes(starttime, endtime)
            if starttime > int(time.time() + timedelta_to_seconds(
                                            datetime.timedelta(weeks=6))):
                logger.error('There are not enough nodes on %s for your ' +
                             'experiments, abort ...', self.cluster)
                exit()