How to use the pyfuse3.getxattr function in pyfuse3

def blocking_umount(mountpoint):
    '''Invoke fusermount and wait for daemon to terminate.'''

    with open('/dev/null', 'wb') as devnull:
        if subprocess.call(['fuser', '-m', mountpoint], stdout=devnull,
                           stderr=devnull) == 0:
            raise MountInUseError(mountpoint)

    ctrlfile = os.path.join(mountpoint, CTRL_NAME)

    log.debug('Flushing cache...')
    pyfuse3.setxattr(ctrlfile, 's3ql_flushcache!', b'dummy')

    # Get pid
    log.debug('Trying to get pid')
    pid = parse_literal(pyfuse3.getxattr(ctrlfile, 's3ql_pid?'), int)
    log.debug('PID is %d', pid)

    # Get command line to make race conditions less-likely
    cmdline = get_cmdline(pid)

    # Unmount
    log.debug('Unmounting...')

    if os.getuid() == 0 or platform.system() == 'Darwin':
        # MacOS X always uses umount rather than fusermount
        umount_cmd = ['umount', mountpoint]
    else:
        umount_cmd = ['fusermount', '-u', mountpoint]

    if subprocess.call(umount_cmd) != 0:
        raise UmountSubError(mountpoint)

args = sys.argv[1:]

    options = parse_args(args)
    setup_logging(options)

    if options.raw:
        pprint = lambda x: '%d bytes' % x
    else:
        pprint = pretty_print_size

    ctrlfile = assert_fs_owner(options.mountpoint, mountpoint=True)

    # Use a decent sized buffer, otherwise the statistics have to be
    # calculated three(!) times because we need to invoke getxattr
    # three times.
    buf = pyfuse3.getxattr(ctrlfile, 's3qlstat', size_guess=256)

    (entries, blocks, inodes, fs_size, dedup_size,
     compr_size, db_size, cache_cnt, cache_size, dirty_cnt,
     dirty_size, removal_cnt) = struct.unpack('QQQQQQQQQQQQ', buf)
    p_dedup = dedup_size * 100 / fs_size if fs_size else 0
    p_compr_1 = compr_size * 100 / fs_size if fs_size else 0
    p_compr_2 = compr_size * 100 / dedup_size if dedup_size else 0
    print ('Directory entries:    %d' % entries,
           'Inodes:               %d' % inodes,
           'Data blocks:          %d' % blocks,
           'Total data size:      %s' % pprint(fs_size),
           'After de-duplication: %s (%.2f%% of total)'
             % (pprint(dedup_size), p_dedup),
           'After compression:    %s (%.2f%% of total, %.2f%% of de-duplicated)'
             % (pprint(compr_size), p_compr_1, p_compr_2),
           'Database size:        %s (uncompressed)' % pprint(db_size),