public function activatePart(
        $invNo, $pclass = KlarnaPClass::INVOICE, $clear = true
    ) {
        $this->_checkInvNo($invNo);
        $this->_checkArtNos($this->artNos);

        self::printDebug('activate_part artNos array', $this->artNos);

        //function activate_part_digest
        $string = $this->_eid . ":" . $invNo . ":";
        foreach ($this->artNos as $artNo) {
            $string .= $artNo["artno"] . ":". $artNo["qty"] . ":";
        }
        $digestSecret = self::digest($string . $this->_secret);
        //end activate_part_digest

        $paramList = array(
            $this->_eid,
            $invNo,
            $this->artNos,
            $digestSecret,
            $pclass,
            $this->shipInfo
        );

        self::printDebug('activate_part array', $paramList);

        $result = $this->xmlrpc_call('activate_part', $paramList);

        if ($clear === true) {
            $this->clear();
        }

        self::printDebug('activate_part result', $result);

        return $result;
    }