def get_credit_taxonomy(contrib_element):
    """Get the contributor roles from the CREDiT taxonomy element when it is present.
    Right now, this is is equivalent to author roles.
    For more information about this data structure, see http://dictionary.casrai.org/Contributor_Roles
    :param contrib_element: An article XML element with the tag <contrib>
    :return: dictionary of contributor roles for an individual contributor

    """
    credit_dict = {}
    for item in contrib_element.getchildren():
        if item.tag == 'role':
            content_type = item.attrib.get('content-type', None)
            if content_type == 'http://credit.casrai.org/':
                content_type = 'CASRAI CREDiT taxonomy'
            role = item.text
            if not credit_dict.get(content_type, None):
                credit_dict[content_type] = [role]
            else:
                credit_dict[content_type].append(role)
    return credit_dict