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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 ls_(get_size=True):
    '''
    List SCSI devices, with details

    CLI Examples:

    .. code-block:: bash

        salt '*' scsi.ls
        salt '*' scsi.ls get_size=False

    get_size : True
        Get the size information for scsi devices.  This option
        should be set to False for older OS distributions (RHEL6 and older)
        due to lack of support for the '-s' option in lsscsi.

        .. versionadded:: 2015.5.10
    '''

    if not salt.utils.path.which('lsscsi'):
        __context__['retcode'] = 1
        return 'scsi.ls not available - lsscsi command not found'

    if get_size:
        cmd = 'lsscsi -dLsv'
    else:
        cmd = 'lsscsi -dLv'

    ret = {}
    res = __salt__['cmd.run_all'](cmd)
    rc = res.get('retcode', -1)
    if rc != 0:
        __context__['retcode'] = rc
        error = res.get('stderr', '').split('\n')[0]
        if error == "lsscsi: invalid option -- 's'":
            return '{0} - try get_size=False'.format(error)
        return res.get('stderr', '').split('\n')[0]
    data = res.get('stdout', '')

    for line in data.splitlines():
        if line.startswith('['):
            size = None
            major = None
            minor = None
            comps = line.strip().split()
            key = comps[0]
            if get_size:
                size = comps.pop()
            majmin = comps.pop()
            if majmin.startswith('['):
                major, minor = majmin.replace('[', '').replace(']', '').split(':')
            device = comps.pop()
            model = ' '.join(comps[3:])
            ret[key] = {
                'lun': key.replace('[', '').replace(']', ''),
                'size': size,
                'major': major,
                'minor': minor,
                'device': device,
                'model': model,
            }
        elif line.startswith(' '):
            if line.strip().startswith('dir'):
                comps = line.strip().split()
                ret[key]['dir'] = [
                    comps[1],
                    comps[2].replace('[', '').replace(']', '')
                ]
            else:
                comps = line.strip().split('=')
                ret[key][comps[0]] = comps[1]
    return ret