code: private function getInterfaceSubscribers(SubscriberInterface $interface)
      {
          $subscribers = array();
          foreach ($interface->getSubscriptions() as $eventName => $mixed) {
              if (\is_string($mixed)) {
                  // methodName
                  $subscribers[] = array($eventName, array($interface, $mixed), 0);
              } elseif (\count($mixed) == 2 && \is_int($mixed[1])) {
                  // array('methodName', priority)
                  $subscribers[] = array($eventName, array($interface, $mixed[0]), $mixed[1]);
              } else {
                  foreach ($mixed as $mixed2) {
                      // methodName
                      // or array(methodName[, priority])
                      if (\is_string($mixed2)) {
                          $callable = array($interface, $mixed2);
                          $priority = 0;
                      } else {
                          $callable = array($interface, $mixed2[0]);
                          $priority = isset($mixed2[1]) ? $mixed2[1] : 0;
                      }
                      $subscribers[] = array($eventName, $callable, $priority);
                  }
              }
          }
          return $subscribers;
      }
docs: Calls the passed object's getSubscriptions() method and returns a normalized list of subscriptions
  
  @param SubscriberInterface $interface object implementing subscriber interface
  
  @return array