GraphQL\Examples\Blog\Data\DataSource::findUser PHP Method

    public static function findUser($id)
    {
        return isset(self::$users[$id]) ? self::$users[$id] : null;
    }

 public function author(Comment $comment)
 {
     if ($comment->isAnonymous) {
         return null;
     }
     return DataSource::findUser($comment->authorId);
 }