public function restrictToDataboxes($databoxes)
    {
        if ($this->collections) {
            throw new \LogicException('You can not restrict on databoxes and collections simultanously');
        }

        $this->databoxes = [];

        foreach ($this->toIterator($databoxes) as $databox) {
            if (!$databox instanceof \databox) {
                throw new \InvalidArgumentException('Restrict to databoxes only accept databoxes as argument');
            }
            $this->databoxes[] = $databox;
        }

        return $this->databoxes;
    }