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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def rescan_all(host):
    '''
    List scsi devices

    CLI Example:

    .. code-block:: bash

        salt '*' scsi.rescan_all 0
    '''
    if os.path.isdir('/sys/class/scsi_host/host{0}'.format(host)):
        cmd = 'echo "- - -" > /sys/class/scsi_host/host{0}/scan'.format(host)
    else:
        return 'Host {0} does not exist'.format(host)
    return __salt__['cmd.run'](cmd).splitlines()