How to use the foxdriver.launch function in foxdriver

var launchCfg = {
      url: defaultLaunchURL,
      bin: opts.executablePath || '',
      args: []
    };

    if (opts.headless) {
      launchCfg.args.push('--headless');
    }

    if (opts.userDataDir) {
      launchCfg.args.push('--profile');
      launchCfg.args.push(opts.userDataDir);
    }

    const { browser: fdBrowser, tab: fdTab } = await foxdriver.launch(launchCfg);

    if (opts.throttling) {
      const downloadThroughput = opts.throttling.downloadThroughput || 75000
      const uploadThroughput = opts.throttling.uploadThroughput || 25000
      const latency = opts.throttling.latency || 100
      await fdTab.emulation.setNetworkThrottling(downloadThroughput, uploadThroughput, latency);
    }

    return new browser({fdBrowser, fdTab});
	}
}

constructor(launcher, throttler) {

        super()[_throttler_] = throttler;

        this.open = true;

        this[_remote_] = FoxDriver.launch( launcher ).then(
            ({ browser })  =>  browser
        );
    }