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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 mangle_volume(citation_elements):
 """Make sure the volume letter is before the volume number e.g. transforms 100B to B100 """

    volume_re = re.compile(ur"(\d+)([A-Z])", re.U | re.I)
    for el in citation_elements:
        if el['type'] == 'JOURNAL':
            matches = volume_re.match(el['volume'])
            if matches:
                el['volume'] = matches.group(2) + matches.group(1)

    return citation_elements