RSS Feed/News Undefined method 'array_map'

[ENXF NET]

I'm getting error "undefined method array_map" in my function.
Should I import some class in order to work? Or any special xf tag to loop in query results?

PHP
Code:

public function actionExpire()
    {
        $books = $this->finder('FOX\Books:Book')->where('status', 'valid')->fetch();
        $books->array_map(
            function($book) {
                if ($book->expiration < time())
                {
                    $book->status = 'expired';
                    $book->save()...

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