How to use the aexpect.kill_tail_threads function in aexpect

# Kill all unresponsive VMs
    if params.get("kill_unresponsive_vms") == "yes":
        logging.debug("Param 'kill_unresponsive_vms' specified, killing all "
                      "VMs that fail to respond to a remote login request")
        for vm in env.get_all_vms():
            if vm.is_alive():
                try:
                    session = vm.login()
                    session.close()
                except (remote.LoginError, virt_vm.VMError), e:
                    logging.warn(e)
                    vm.destroy(gracefully=False)

    # Kill all aexpect tail threads
    aexpect.kill_tail_threads()

    # Terminate tcpdump if no VMs are alive
    living_vms = [vm for vm in env.get_all_vms() if vm.is_alive()]
    if not living_vms and "tcpdump" in env:
        env["tcpdump"].close()
        del env["tcpdump"]

    if params.get("setup_hugepages") == "yes":
        h = test_setup.HugePageConfig(params)
        h.cleanup()
        if params.get("vm_type") == "libvirt":
            libvirt_vm.libvirtd_restart()

    if params.get("setup_thp") == "yes":
        thp = test_setup.TransparentHugePageConfig(test, params)
        thp.cleanup()

destroy = False
        vm_params = params.object_params(vm.name)
        for image in vm_params.objects('images'):
            if params.object_params(image).get('remove_image') == 'yes':
                destroy = True
        if destroy and not vm.is_dead():
            logging.debug(
                'Image of VM %s was removed, destroying it.',
                vm.name)
            vm.destroy()

    # Terminate the ip sniffer thread
    env.stop_ip_sniffing()

    # Kill all aexpect tail threads
    aexpect.kill_tail_threads()

    # collect sosreport of host/remote host during postprocess if enabled
    if params.get("enable_host_sosreport", "no") == "yes":
        sosreport_path = utils_misc.get_sosreport(sosreport_name="host")
        logging.info("Sosreport for host: %s", sosreport_path)
    if params.get("enable_remote_host_sosreport", "no") == "yes":
        remote_params = {'server_ip': params['remote_ip'], 'server_pwd': params['remote_pwd']}
        remote_params['server_user'] = params['remote_user']
        session = test_setup.remote_session(remote_params)
        sosreport_path = utils_misc.get_sosreport(session=session,
                                                  remote_ip=params['remote_ip'],
                                                  remote_pwd=params['remote_pwd'],
                                                  remote_user=params['remote_user'],
                                                  sosreport_name="host_remote")
        logging.info("Sosreport for remote host: %s", sosreport_path)
    living_vms = [vm for vm in env.get_all_vms() if vm.is_alive()]

destroy = False
        vm_params = params.object_params(vm.name)
        for image in vm_params.objects('images'):
            if params.object_params(image).get('remove_image') == 'yes':
                destroy = True
        if destroy and not vm.is_dead():
            logging.debug(
                'Image of VM %s was removed, destroying it.',
                vm.name)
            vm.destroy()

    # Terminate the ip sniffer thread
    env.stop_ip_sniffing()

    # Kill all aexpect tail threads
    aexpect.kill_tail_threads()

    living_vms = [vm for vm in env.get_all_vms() if vm.is_alive()]
    # Close all monitor socket connections of living vm.
    for vm in living_vms:
        if hasattr(vm, "monitors"):
            for m in vm.monitors:
                try:
                    m.close()
                except Exception:
                    pass
        # Close the serial console session, as it'll help
        # keeping the number of filedescriptors used by avocado-vt honest.
        vm.cleanup_serial_console()

    libvirtd_inst = utils_libvirtd.Libvirtd()
    vm_type = params.get("vm_type")

glob.glob(os.path.join(test.debugdir, '*.webm'))):
            os.unlink(f)

    # Kill all unresponsive VMs
    if params.get("kill_unresponsive_vms") == "yes":
        for vm in env.get_all_vms():
            if vm.is_alive():
                try:
                    session = vm.login()
                    session.close()
                except (remote.LoginError, virt_vm.VMError), e:
                    logging.warn(e)
                    vm.destroy(gracefully=False)

    # Kill all aexpect tail threads
    aexpect.kill_tail_threads()

    # Terminate tcpdump if no VMs are alive
    living_vms = [vm for vm in env.get_all_vms() if vm.is_alive()]
    if not living_vms and "tcpdump" in env:
        env["tcpdump"].close()
        del env["tcpdump"]

    if params.get("setup_hugepages") == "yes":
        h = test_setup.HugePageConfig(params)
        h.cleanup()
        if params.get("vm_type") == "libvirt":
            libvirt_vm.libvirtd_restart()

    if params.get("setup_thp") == "yes":
        thp = test_setup.TransparentHugePageConfig(test, params)
        thp.cleanup()