How to use the pyperf._utils.read_first_line function in pyperf

def get_cpu_temperature(path, cpu_temp):
    hwmon_name = read_first_line(os.path.join(path, 'name'))
    if not hwmon_name.startswith('coretemp'):
        return

    index = 1
    while True:
        template = os.path.join(path, "temp%s_%%s" % index)

        try:
            temp_label = read_first_line(template % 'label', error=True)
        except IOError:
            break

        temp_input = read_first_line(template % 'input', error=True)
        temp_input = float(temp_input) / 1000
        # On Python 2, u"%.0f\xb0C" introduces unicode errors if the
        # locale encoding is ASCII, so use a space.
        temp_input = "%.0f C" % temp_input

        item = '%s:%s=%s' % (hwmon_name, temp_label, temp_input)
        cpu_temp.append(item)

        index += 1

path = os.path.join(sys_cpu_path, "cpu%s/cpufreq/scaling_driver" % cpu)
    scaling_driver = read_first_line(path)
    if scaling_driver:
        info.append('driver:%s' % scaling_driver)

    if scaling_driver == 'intel_pstate':
        path = os.path.join(sys_cpu_path, "intel_pstate/no_turbo")
        no_turbo = read_first_line(path)
        if no_turbo == '1':
            info.append('intel_pstate:no turbo')
        elif no_turbo == '0':
            info.append('intel_pstate:turbo')

    path = os.path.join(sys_cpu_path, "cpu%s/cpufreq/scaling_governor" % cpu)
    scaling_governor = read_first_line(path)
    if scaling_governor:
        info.append('governor:%s' % scaling_governor)

    return info

def get_isolated_cpus():
    """Get the list of isolated CPUs.

    Return a sorted list of CPU identifiers, or return None if no CPU is
    isolated.
    """
    # The cpu/isolated sysfs was added in Linux 4.2
    # (commit 59f30abe94bff50636c8cad45207a01fdcb2ee49)
    path = sysfs_path('devices/system/cpu/isolated')
    isolated = read_first_line(path)
    if isolated:
        return parse_cpu_list(isolated)

    cmdline = read_first_line(proc_path('cmdline'))
    if cmdline:
        match = re.search(r'\bisolcpus=([^ ]+)', cmdline)
        if match:
            isolated = match.group(1)
            return parse_cpu_list(isolated)

    return None

isolated = get_isolated_cpus()
    if isolated:
        isolated = set(isolated)

    configs = {}
    for cpu in cpus:
        config = get_cpu_config(cpu)
        if nohz_full and cpu in nohz_full:
            config.append('nohz_full')
        if isolated and cpu in isolated:
            config.append('isolated')
        if config:
            configs[cpu] = ', '.join(config)
    config = format_cpu_infos(configs)

    cpuidle = read_first_line('/sys/devices/system/cpu/cpuidle/current_driver')
    if cpuidle:
        config.append('idle:%s' % cpuidle)

    if not config:
        return
    metadata['cpu_config'] = '; '.join(config)

def get_cpu_config(cpu):
    sys_cpu_path = sysfs_path("devices/system/cpu")
    info = []

    path = os.path.join(sys_cpu_path, "cpu%s/cpufreq/scaling_driver" % cpu)
    scaling_driver = read_first_line(path)
    if scaling_driver:
        info.append('driver:%s' % scaling_driver)

    if scaling_driver == 'intel_pstate':
        path = os.path.join(sys_cpu_path, "intel_pstate/no_turbo")
        no_turbo = read_first_line(path)
        if no_turbo == '1':
            info.append('intel_pstate:no turbo')
        elif no_turbo == '0':
            info.append('intel_pstate:turbo')

    path = os.path.join(sys_cpu_path, "cpu%s/cpufreq/scaling_governor" % cpu)
    scaling_governor = read_first_line(path)
    if scaling_governor:
        info.append('governor:%s' % scaling_governor)

def get_cpu_temperature(path, cpu_temp):
    hwmon_name = read_first_line(os.path.join(path, 'name'))
    if not hwmon_name.startswith('coretemp'):
        return

    index = 1
    while True:
        template = os.path.join(path, "temp%s_%%s" % index)

        try:
            temp_label = read_first_line(template % 'label', error=True)
        except IOError:
            break

        temp_input = read_first_line(template % 'input', error=True)
        temp_input = float(temp_input) / 1000
        # On Python 2, u"%.0f\xb0C" introduces unicode errors if the
        # locale encoding is ASCII, so use a space.
        temp_input = "%.0f C" % temp_input

        item = '%s:%s=%s' % (hwmon_name, temp_label, temp_input)
        cpu_temp.append(item)

        index += 1