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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 update_user(bridge_user):
 """ Update only the user attributes provided. Return a list of BridgeUsers objects with custom fields. """

    if bridge_user.bridge_id:
        url = author_id_url(bridge_user.bridge_id)
    else:
        url = author_uid_url(bridge_user.netid)
    resp = patch_resource(url + ("?%s" % CUSTOM_FIELD),
                          json.dumps(bridge_user.to_json_patch(),
                                     separators=(',', ':')))
    return _process_json_resp_data(resp)