Assert class instances of collection items

modules/opd_presentations/src/Events.php

@@ -4,6 +4,9 @@ declare(strict_types=1);
 
 namespace Drupal\opd_presentations;
 
+use Webmozart\Assert\Assert;
+
+
 /**
  * @implements \IteratorAggregate<Event>
  */
@@ -13,6 +16,7 @@ readonly final class Events implements \IteratorAggregate {
   * @param Event[] $events
   */
   private function __construct(private array $events) {
+    Assert::allIsInstanceOf($events, Event::class);
   }
 
   public function filter(\Closure $callback): self {