test.js

const services = require('@jupyterlab/services');

var DEFAULT_OPTIONS = {
"kernelName": "python",
"path": "/tmp/foo.ipynb",
"serverSettings" : services.ServerConnection.makeSettings({
  "baseUrl" :  process.env.JUPYTER_BASEURL ||  "http://127.0.0.1:8889",
  "wsUrl": process.env.JUPYTER_WSURL || "http://127.0.0.1:8889",
 "token": '',
})
};

let options = {...DEFAULT_OPTIONS, path: `/tmp/workspace/${id}`};

let session;

let run = new Promise((resolve, reject) => {

  services.Session.startNew(options).then(async (s) => {

  session = s;

  const future = session.kernel.requestExecute({ code: code })
  future.onIOPub = function(msg) {
    console.log(websocket);

  };

  future.onReply = function(reply) {
    console.log('Got execute reply', reply);
  };

  return future.done
}).then(() => {
  return session.shutdown()
}).then(() => {
  log.info("Session Shutdown")
  resolve()
  })

run()