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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 list_tab(user):
    '''
    Return the contents of the specified user's incrontab

    CLI Example:

    .. code-block:: bash

        salt '*' incron.list_tab root
    '''
    if user == 'system':
        data = raw_system_incron()
    else:
        data = raw_incron(user)
        log.debug('incron user data %s', data)
    ret = {'crons': [],
           'pre': []
           }
    flag = False
    comment = None
    tag = '# Line managed by Salt, do not edit'
    for line in data.splitlines():
        if line.endswith(tag):
            if len(line.split()) > 3:
                # Appears to be a standard incron line
                comps = line.split()
                path = comps[0]
                mask = comps[1]
                (cmd, comment) = ' '.join(comps[2:]).split(' # ')

                dat = {'path': path,
                       'mask': mask,
                       'cmd': cmd,
                       'comment': comment}
                ret['crons'].append(dat)
                comment = None
        else:
            ret['pre'].append(line)
    return ret