public function store($code, $label, $country_id = null, $country_code = null)
    {
        $fields = [];
        //@todo validate params, throw exception when they are missing
        $fields['code'] = $code;
        $fields['label'] = $label;
        if (!is_null($country_id)) $fields['country_id'] = $country_id;
        if (!is_null($country_code)) $fields['country_code'] = $country_code;

        return $this->_post($fields);
    }