public function thumbnail($type = 'auto')
    {
        if ($type !== 'auto' && !\in_array($type, $this->thumbnailTypes, true)) {
            return $this;
        }

        if ($this->thumbnailType !== $type) {
            $this->_thumbnail = null;
        }

        $this->thumbnailType = $type;

        return $this;
    }