def METHOD_NAME():
    """
    prepare an invalid xml with video device containing
    invalid attribute "foot", for example,
    <model type='qxl' ram='65536' vram='65536' vgamem='65536' foot='3'/>
    """
    new_xml = xml_backup.copy()
    # Add video device if guest doesn't have
    if not new_xml.get_devices(device_type="video"):
        logging.debug("Guest doesn't have video device, add one")
        new_video = Video()
        new_video.model_type = "virtio"
        new_xml.add_device(new_video)
        logging.debug("The xml with video is %s", new_xml)
    # Set invalid attribute for video device
    video_device_xml = new_xml.xmltreefile.find('/devices/video/model')
    if video_device_xml is None:
        test.error("Failed to get guest video device")
    video_device_xml.set("foot", "3")
    logging.debug("The new xml used for defining a new domain is %s", new_xml)
    xml_file = new_xml.xmltreefile.name
    # undefine the original vm
    virsh.undefine(vm_name, options='--nvram')
    return xml_file