def _normalize_mlengine_job_id(job_id):
    """
    
    """

    # Add a prefix when a job_id starts with a digit or a template
    match = re.search(r'\d|\{{2}', job_id)
    if match and match.start() == 0:
        job = 'z_{}'.format(job_id)
    else:
        job = job_id

    # Clean up 'bad' characters except templates
    tracker = 0
    cleansed_job_id = ''
    for m in re.finditer(r'\{{2}.+?\}{2}', job):
        cleansed_job_id += re.sub(r'[^0-9a-zA-Z]+', '_',
                                  job[tracker:m.start()])
        cleansed_job_id += job[m.start():m.end()]
        tracker = m.end()

    # Clean up last substring or the full string if no templates
    cleansed_job_id += re.sub(r'[^0-9a-zA-Z]+', '_', job[tracker:])

    return cleansed_job_id