php - SilverStripe: How do I insert a tab before another tab? -

i trying insert new admin tab before root.content.main without luck. i've tried:

$fields->insertbefore(new tab('root.content.overview', 'overview'), 'root.content.main'); 

and

$fields->addfieldtotab('root.content', new tab('overviewtab', 'root.content.overview'), 'root.content.main'); 

without luck.

anyone have ideas? i've hunted through api there isn't explanation how tab naming system works.

figured out...

$fields->insertbefore(new tab('overview', 'project overview'), 'main');