How to set Google TTS language

In the release notes of 2021.12 I saw this:
added support for ms-MY, nl-BE, pa-IN to Google TTS.

As I live in Belgium I would like to use the nl-BE option, as I prefer a Belgian voice to a Dutch one.
But I’m unable to find anything in the docs or release note that explains how to use this.

If I change the language in my configuration.yaml from ‘nl’ to ‘nl-BE’ it produces an error.

maybe this helps…