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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_users(runas=None):
    '''
    Return a list of users based off of rabbitmqctl user_list.

    CLI Example:

    .. code-block:: bash

        salt '*' rabbitmq.list_users
    '''
    # Windows runas currently requires a password.
    # Due to this, don't use a default value for
    # runas in Windows.
    if runas is None and not salt.utils.platform.is_windows():
        runas = salt.utils.user.get_user()
    res = __salt__['cmd.run_all'](
        [RABBITMQCTL, 'list_users', '-q'],
        reset_system_locale=False,
        runas=runas,
        python_shell=False)

    # func to get tags from string such as "[admin, monitoring]"
    func = lambda string: [x.strip() for x in string[1:-1].split(',')] if ',' in string else [x for x in
                                                                                              string[1:-1].split(' ')]
    return _output_to_dict(res, func)