def tmux_id_4_restore(tmux_id):
    #if no backup exists, exit application
    all_bk =util.all_backups() 
    if len(all_bk)<1:
        LOG.error('(retore -r): backup dir is empty, nothing to restore')
        sys.exit(1)

    #checking tmux_id
    if tmux_id:
        if tmux_id not in all_bk:
            LOG.error('(restore -r): cannot find given backup name:%s'% tmux_id)
            sys.exit(1)
    else:
        tmux_id = util.latest_backup().split('/')[-1]
        print 'backup name is empty, using last backup:%s'%tmux_id

    return tmux_id
Returns:
dataset/ETHPy150Open sk1418/retmux/tmuxbk/controller.py/tmux_id_4_restore--crossover with--dataset/ETHPy150Open meraki-analytics/cassiopeia/cassiopeia/type/core/match.py/ParticipantTimeline.spider_assists_per_min_counts