def create_part_xml(part_msg_list=None):
    """
    get information from part_msg_list and covert it to xml.
    part_msg_list has special format.
    """
    if not part_msg_list:
        part_msg_list = []
    xml_string = '<CompleteMultipartUpload>'
    for part in part_msg_list:
        if len(part) >= 3:
            xml_string += '<Part>'
            xml_string += '<PartNumber>' + str(part[0]) + '</PartNumber>'
            xml_string += '<ETag>"' + str(part[2]).upper() + '"</ETag>'
            xml_string += '</Part>'
        else:
            print('the ', part, ' in part_msg_list is not as expected!')
            return ''
    xml_string += '</CompleteMultipartUpload>'
    return xml_string
