private function assertValidSuppression(array $suppression)
    {
        if (isset($suppression['suppress_on'])) {
            if(isset($suppression['suppress_on']['campaign']))
                $this->assertValidCampaign($suppression['suppress_on']['campaign']);
            if(isset($suppression['suppress_on']['transaction']))
                $this->assertValidTransaction($suppression['suppress_on']['transaction']);
        }
    }