How to access commerce attribute's value in a Oppty Import Result Parser?

Summary:

Hi Team,

We've a requirement where we wanted to update a transaction level attribute from oppty only when its value is blank on the quote. For this, in the Oppty Import XSL, In the SOAP generator I'm able to query the salesforce field, but in the parser I'm unable to fetch the transaction attribute value to check whether it's blank or not, accordingly I'll need to create the attribute tag. Below is a sample snippet I'm using. Could anyone please suggest what is going wrong here?

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"