prefill checkbox « Gravity Support Forums

hi,

I'm trying to prefill a form.
I found this: http://www.gravityhelp.com/documentation/page/Gform_field_value_$parameter_name

But I cant get it to work with (more then one) checkbox. text input/areas are fine
How does that work?

I use this tweakes prefill the text inputs/areas:

$value = 'prefill value';
add_filter('gform_field_value_FIELDNAME, function($content) use ($value) {
    return $value;
});

assuming my prefil name for the checkboxes is 'branche' and some example values are: ictmul, indust, archit

$values = array('archit', 'ictmul');
add_filter('gform_field_value_branche, function($content) use ($values) {
    //what goes here?
    return $values;//?? some array() ??
});