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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 mdadm():
    '''
    Return list of mdadm devices
    '''
    devices = set()
    try:
        with salt.utils.files.fopen('/proc/mdstat', 'r') as mdstat:
            for line in mdstat:
                line = salt.utils.stringutils.to_unicode(line)
                if line.startswith('Personalities : '):
                    continue
                if line.startswith('unused devices:'):
                    continue
                if ' : ' in line:
                    devices.add(line.split(' : ')[0])
    except IOError:
        return {}

    devices = sorted(devices)
    if devices:
        log.trace('mdadm devices detected: %s', ', '.join(devices))

    return {'mdadm': devices}