How to use the ibm-watson/speech-to-text/v1.URL function in ibm-watson

);

// set up webpack-dev-middleware to serve Webpack bundles for examples
const compiler = webpack(webpackConfig);
app.use(
  webpackDevMiddleware(compiler, {
    publicPath: '/' // Same as `output.publicPath` in most cases.
  })
);

const sttCredentials = Object.assign(
  {
    username: process.env.SPEECH_TO_TEXT_USERNAME, // or hard-code credentials here
    password: process.env.SPEECH_TO_TEXT_PASSWORD,
    iam_apikey: process.env.SPEECH_TO_TEXT_IAM_APIKEY, // if using an RC service
    url: process.env.SPEECH_TO_TEXT_URL ? process.env.SPEECH_TO_TEXT_URL : SpeechToTextV1.URL
  },
  vcapServices.getCredentials('speech_to_text') // pulls credentials from environment in bluemix, otherwise returns {}
);

// speech to text token endpoint
app.use('/api/speech-to-text/token', function(req, res) {
  const sttAuthService = new AuthorizationV1(sttCredentials);
  sttAuthService.getToken(function(err, response) {
    if (err) {
      console.log('Error retrieving token: ', err);
      res.status(500).send('Error retrieving token');
      return;
    }
    const token = response.token || response;
    if (process.env.SPEECH_TO_TEXT_IAM_APIKEY) {
      res.json({ accessToken: token, url: sttCredentials.url });