public function mapType($ctype)
    {
        if (is_array($ctype)) {
            return array_map([$this, 'mapType'], $ctype);
        }

        foreach ($this->_mimeTypes as $alias => $types) {
            if (in_array($ctype, (array)$types)) {
                return $alias;
            }
        }

        return null;
    }