i have REST API made in node and express. It looks like operators aren't imported (i have tried few operators) and i don't know why it throws error on `async-db.js`. I have tried, importing operators on all the ways i could think of, but no success, also i installed `rxjs-compat` as you can see in my `package.json`. Observable and Subject are working fine, and i dont know what am i doing wrong. I have used imports like this many times in Angular client app, and everything worked fine.

. 
My file structure looks like this:

```
+ app.js
+ async-db.js
++ routes/routes.js

```

My code looks like this: 

```
import { Observable, Subject, from, of} from 'rxjs';
import { map, retryWhen, delay, retry, retryTime } from 'rxjs/operators';
export function t2tObservable({ db, name, param }) {
  let retryTime = 125;
  let subject = new Subject();
  let dbRef = db.ref(param ? name + "/" + param : name);
  dbRef.once("value", (snap) => {
    if (snap.val()) {
      subject.next(snap.val());
      subject.complete();
    }
    else {
     subject.error(new Error("T2TError: no data"));
    }
   }, (e) => {
     subject.error(e);
     console.log("The read failed: " + e.code);
   });
   return subject.asObservable().retryWhen(function (errors) {
     retryTime *= 2;
     return errors.delay(retryTime);
   });
 }

```

And the error looks like this:

```
return subject.asObservable().retryWhen(function (errors) {
                            ^
TypeError: subject.asObservable(...).retryWhen is not a function
at Object.t2tObservable (...\t2tauthapi\dist\async-db.js:33:33)
at Object.<anonymous> (...\t2tauthapi\dist\routes\routes.js:36:9)
at Module._compile (module.js:652:30)
at Object.Module._extensions..js (module.js:663:10)
at Module.load (module.js:565:32)
at tryModuleLoad (module.js:505:12)
at Function.Module._load (module.js:497:3)
at Module.require (module.js:596:17)
at require (internal/module.js:11:18)
at Object.<anonymous> (...\t2tauthapi\dist\app.js:7:14)

```

My package.json looks like this

```
{
  "name": "t2tauthapi",
  "version": "1.0.0",
  "description": "",
  "main": "app.js",
  "scripts": {
  "test": "echo \"Error: no test specified\" && exit 1",
  "build": "rimraf dist/ && babel ./ --out-dir dist/ --ignore 
    ./node_modules,./.babelrc,./package.json,./npm-debug.log --copy-files",
    "start": "npm run build && node dist/app.js"
  },
  "author": "Toni Beverin",
  "license": "ISC",
  "dependencies": {
  "body-parser": "^1.18.2",
  "cors": "^2.8.4",
  "express": "^4.16.3",
  "firebase-admin": "^5.12.0",
  "jsonwebtoken": "^8.2.1",
  "lodash": "^4.17.10",
  "rxjs": "^6.1.0",
  "rxjs-compat": "^6.1.0"
},
"devDependencies": {
  "babel-cli": "^6.26.0",
  "babel-preset-es2015": "^6.24.1",
  "rimraf": "^2.6.2"
  }
}

```