Azure: how to authenticate service api call

Am trying to call notificationHub service api using node.js SDK. I generated key "token" following this page of documentation

Then in my node.js app i had the following code:

  const client = new notificationHubsClient(AZURE_KEY, AZURE_SUBSCRIPTION_ID);
  console.log('the client', client);

However i got this error:

UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): Error: credentials argument needs to implement signRequest method

So far am using the token i generated previously as credentials not sure if that correct, from the docs:

var client = new notificationHubsClient(credentials, 'your-subscription-id');

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