public function unserialize($serialized = null)
    {

        // initialize the array for the unserialized additional attributes
        $attributes = array();

        // explode the additional attributes
        if ($additionalAttributes = $this->explode($serialized)) {
            // iterate over the attributes and append them to the row
            foreach ($additionalAttributes as $additionalAttribute) {
                // explode attribute code/option value from the attribute
                list ($attributeCode, $optionValue) = explode('=', $additionalAttribute);

                // extract the key/value pairs into an array
                $attributes[$attributeCode] = $optionValue;
            }
        }

        // return the array with the unserialized additional attributes
        return $attributes;
    }