/**
  * @param SubscriptionInterface $subscription
  * @param array $options
  * @return array
  */
 public function serializeSubscription(SubscriptionInterface $subscription, $options = array())
 {
     $result = array();
     if ($subscription->getPlan() && $subscription->getPlan()->getSubscriptionPlanId()) {
         $result['planId'] = $subscription->getPlan()->getSubscriptionPlanId();
     }
     if ($subscription->getCustomer() && count($subscription->getCustomer()->getCreditCards()) > 0) {
         $cards = $subscription->getCustomer()->getCreditCards();
         //In case there is no default card, take the first
         $result['paymentMethodToken'] = $cards->first()->getToken();
         //set default credit card as default
         foreach ($cards as $card) {
             if ($card->isDefault()) {
                 $result['paymentMethodToken'] = $card->getToken();
             }
         }
     }
     if (count($options) > 0) {
         $result['options'] = $options;
     }
     return $result;
 }