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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 _walk_through(job_dir, display_progress=False):
    '''
    Walk through the job dir and return jobs
    '''
    serial = salt.payload.Serial(__opts__)

    for top in os.listdir(job_dir):
        t_path = os.path.join(job_dir, top)

        for final in os.listdir(t_path):
            load_path = os.path.join(t_path, final, '.load.p')
            with salt.utils.files.fopen(load_path, 'rb') as rfh:
                job = serial.load(rfh)

            if not os.path.isfile(load_path):
                continue

            with salt.utils.files.fopen(load_path, 'rb') as rfh:
                job = serial.load(rfh)
            jid = job['jid']
            if display_progress:
                __jid_event__.fire_event(
                    {'message': 'Found JID {0}'.format(jid)},
                    'progress'
                )
            yield jid, job, t_path, final