/**
  * When a member cancels a subscription we need to notify Stripe to also
  * cancel the Stripe subscription.
  *
  * @since  1.0.0
  * @param MS_Model_Relationship $subscription The membership relationship.
  */
 public function cancel_membership($subscription)
 {
     parent::cancel_membership($subscription);
     $this->_api->set_gateway($this);
     $customer = $this->_api->find_customer($subscription->get_member());
     $membership = $subscription->get_membership();
     $stripe_sub = false;
     if ($customer) {
         $stripe_sub = $this->_api->get_subscription($customer, $membership);
     }
     if ($stripe_sub) {
         $stripe_sub->cancel(array('at_period_end' => true));
     }
 }