Dev Environment access in custom code

Hi,

How can one acces to Dev Environment values from within a custom code ?

Trying this doesn't work, although variables are set OK in Dev Environment settings

class MyAuthInterceptor extends FFApiInterceptor {
    const varValue = String.fromEnvironment("myVar");
    debugPrint("Debug MyAuthInterceptor " + varValue);
    ...
}

I found nothing related in https://docs.flutterflow.io/testing/dev-environments/

Thanks