'Determine the timestamp of the checkpoint, enforcing monotonicity.'

def _checkpoint_timestamp(self):

    timestamp = str(time.time())
    others = glob.glob(os.path.join(self.config.backup_dir, '[0-9]*'))
    others = [os.path.basename(d) for d in others]
    others.append(timestamp)
    others.sort()
    if (others[(-1)] != timestamp):
        timetravel = str((float(others[(-1)]) + 1))
        logger.warning('Current    timestamp    %s    does    not    correspond    to    newest    reverter    checkpoint;    your    clock    probably    jumped.    Time    travelling    to    %s', timestamp, timetravel)
        timestamp = timetravel
    elif ((len(others) > 1) and (others[(-2)] == timestamp)):
        logger.debug('Race    condition    with    timestamp    %s,    incrementing    by    0.01', timestamp)
        timetravel = str((float(others[(-1)]) + 0.01))
        timestamp = timetravel
    return timestamp
