How to bid adjust in Platforms?

[Ken Dan Tinio]

So far I have this but doesn't seem to work

    $devices = new Platform();

    // $devices->setPlatformName('Desktop');

    $devices->setId(30000);

    $biddableAdGroupCriterion = new BiddableAdGroupCriterion();

    $biddableAdGroupCriterion->setAdGroupId(52012184360);

    $biddableAdGroupCriterion->setCriterion($devices);

    $biddableAdGroupCriterion->setBidModifier(1.5);

    $adGroupCriterionOperation = new AdGroupCriterionOperation();

    $adGroupCriterionOperation->setOperand($biddableAdGroupCriterion);

    $adGroupCriterionOperation->setOperator(Operator::SET);

    $operations[] = $adGroupCriterionOperation;   

    $result = $adGroupCriterionService->mutate($operations);