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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 exit_success(jid, ext_source=None):
    '''
    Check if a job has been executed and exit successfully

    jid
        The jid to look up.
    ext_source
        The external job cache to use. Default: `None`.

    CLI Example:

    .. code-block:: bash

        salt-run jobs.exit_success 20160520145827701627
    '''
    ret = dict()

    data = list_job(
        jid,
        ext_source=ext_source
    )

    minions = data.get('Minions', [])
    result = data.get('Result', {})

    for minion in minions:
        if minion in result and 'return' in result[minion]:
            ret[minion] = True if result[minion]['return'] else False
        else:
            ret[minion] = False

    for minion in result:
        if 'return' in result[minion] and result[minion]['return']:
            ret[minion] = True
    return ret