Issue #3456989: Fatal error after Upgrade to Drupal 10.3 and Search API 1.53

src/Plugin/search_api/backend/ElasticSearchBackend.php

@@ -461,12 +461,23 @@ class ElasticSearchBackend extends BackendPluginBase implements PluginFormInterf
    *
    * Make sure that the client does not get serialized.
    */
-  public function __sleep() {
+  public function __sleep(): array {
     $vars = $this->traitSleep();
     unset($vars[array_search('client', $vars)]);
     return $vars;
   }
 
+  /**
+   * {@inheritdoc}
+   *
+   * @todo Method overriding is to support return types in 10.x. Remove
+   * once drupal:10.x support is dropped.
+   */
+  // phpcs:ignore
+  public function __wakeup(): void {
+    parent::__wakeup();
+  }
+
   /**
    * {@inheritdoc}
    */