electron setWindowOpenHandler is not a function

Question

I created an Electron-App for my web-app, which uses SAML. I want to allow the saml window to show up.

So I used the BrowserWindow.WebContents.setWindowOpenHandler function.

I first tried it, where the window object is being instanciated with a new BrowserWindow. That didn't work. I found on GitHub a new method, using the event "web-contents-created"

//Erlaube SAML Authentifizierung, andere Seiten werden blockiert
app.on("web-contents-created", (createEvent, contents) => {
  contents.setWindowOpenHandler(({url}) => {
    if(url.startsWith("https://login.microsoftonline.com/")) {
      return {action: 'allow'};
    }
    else return {action: 'deny'};
  });
});

That didn't word either, I always get the same error messages:

I'm using TypeScript and it's valid code. I'm using Electron 17.1.2

Anyone knows why and how?