How to use the gaiatest.GaiaData function in gaiatest

def run(self, args=sys.argv[1:]):
        args = self.parser.parse_args()

        host, port = args.address.split(':')
        self.marionette = Marionette(host=host, port=int(port))
        self.marionette.start_session()

        self.apps = gaiatest.GaiaApps(self.marionette)
        self.data_layer = gaiatest.GaiaData(self.marionette)
        self.device = gaiatest.GaiaDevice(self.marionette)

        ret = args.func(args)
        if ret is None:
            ret = 0

        self.marionette.delete_session()

        sys.exit(ret)

def __init__(self, marionette, datazilla_config=None, sources=None,
                 log_level='INFO', device_serial=None):
        # Set up logging
        handler = mozlog.StreamHandler()
        handler.setFormatter(mozlog.MozFormatter(include_timestamp=True))
        self.logger = mozlog.getLogger(self.__class__.__name__, handler)
        self.logger.setLevel(getattr(mozlog, log_level.upper()))

        self.device_serial = device_serial
        self.marionette = marionette

        settings = gaiatest.GaiaData(self.marionette).all_settings
        mac_address = self.marionette.execute_script(
            'return navigator.mozWifiManager && '
            'navigator.mozWifiManager.macAddress;')

        self.submit_report = True
        self.ancillary_data = {
            'generated_by': 'b2gperf %s' % __version__,
            'build_url': datazilla_config['build_url']}

        dm = mozdevice.DeviceManagerADB(deviceSerial=self.device_serial)
        self.device = gaiatest.GaiaDevice(self.marionette, manager=dm)

        version = mozversion.get_version(sources=sources, dm_type='adb',
                                         device_serial=self.device_serial)
        self.ancillary_data['build_revision'] = version.get('build_changeset')
        self.ancillary_data['gaia_revision'] = version.get('gaia_changeset')

print ' ** Check to make sure you don\'t have desktop B2G running'
            raise

        apps = GaiaApps(mc)
        apps.kill_all()

        lockscreen = LockScreen(mc)
        lockscreen.unlock()

        if args.wifi_ssid:
            print 'Configuring WiFi'
            if not args.wifi_key or not args.wifi_pass:
                args.error('Missing --wifi_key or --wifi_pass option')
            args.wifi_key = args.wifi_key.upper()

            data_layer = GaiaData(mc)
            data_layer.enable_wifi()
            if args.wifi_key == 'WPA-PSK':
                pass_key = 'psk'
            elif args.wifi_key == 'WEP':
                pass_key = 'wep'
            else:
                args.error('not sure what key to use for %r' % args.wifi_key)

            data = {'ssid': args.wifi_ssid, 'keyManagement': args.wifi_key,
                    pass_key: args.wifi_pass}
            data_layer.connect_to_wifi(data)

        # disconnect marionette client because install_app would need it
        mc.client.close()

        # install apps one by one

def do_login(args):
    mc = get_marionette(args)
    device = GaiaDevice(mc)
    apps = GaiaApps(mc)
    data_layer = GaiaData(mc)

    _persona_frame_locator = ('css selector', "iframe")

    # Trusty UI on home screen
    _tui_container_locator = ('id', 'trustedui-frame-container')

    # Persona dialog
    _waiting_locator = ('css selector', 'body.waiting')
    _email_input_locator = ('id', 'authentication_email')
    _password_input_locator = ('id', 'authentication_password')
    _new_password = ('id', 'password')
    _verify_new_password = ('id', 'vpassword')
    _next_button_locator = ('css selector', 'button.start')
    _verify_start_button = ('css selector', 'button#verify_user')
    _returning_button_locator = ('css selector', 'button.returning')
    _sign_in_button_locator = ('id', 'signInButton')

'/storage/sdcard',
                         '/storage/sdcard0',
                         '/storage/sdcard1']:
                if self.device.file_manager.dir_exists(path):
                    for item in self.device.file_manager.list_items(path):
                        self.device.file_manager.remove('/'.join([path, item]))

        self.logger.debug('Populating databases')
        self.populate_databases()

        if self.restart:
            self.logger.debug('Starting B2G')
            self.device.start_b2g(self.start_timeout)

        self.apps = gaiatest.GaiaApps(self.marionette)
        self.data_layer = gaiatest.GaiaData(self.marionette)

        self.logger.debug('Populating files')
        self.populate_files()

        self.logger.debug('Settling for %d seconds' % self.settle_time)
        time.sleep(self.settle_time)

        self.marionette.switch_to_frame()

        safe_volume = 5
        self.logger.debug('Setting content volume to %d' % safe_volume)
        self.data_layer.set_setting('audio.volume.content', safe_volume)

        self.logger.debug('Switching off keyboard first time use screen')
        self.data_layer.set_setting('keyboard.ftu.enabled', False)