protected function prepareEventManagers(array $managers) {
    $values = NULL;

    foreach ($managers as $uuid) {
      // Load the user(s) by the given uuid(s).
      $load = $this->userStorage->loadByProperties(['uuid' => $uuid]);
      $account = current($load);

      if ($account instanceof User) {
        $properties = [
          'target_id' => $account->id(),
        ];

        $values[] = $properties;
      }
    }
    return $values;
  }