public function logIPNResponse($sLevel, $sMessage, $oIpnMessage = null)
    {
        if ((bool)$this->getConfig()->getConfigParam('blAmazonLogging') !== true) {
            return;
        }

        $aContext = ($oIpnMessage !== null) ? array('ipnMessage' => $oIpnMessage) : array();
        $this->_getLogger()->log($sLevel, $sMessage, $aContext);
    }