Check for applied bills on purchase order sublist line

I have a script (Thank You Nathan Lamb) that prevents deleting a sublist line on Purchase orders when PO is in an approved state.

I need additional functionality to also check if the sublist line has a bill applied to it, if false, then allow delete.

Is this possible and if so what fields/variables do I need to add?

/**
 * @NApiVersion 2.1
 * @NScriptType ClientScript
 */

define(["N/record"], function(record) {

 function validateDelete(scriptContext) {
   // get your current record object
   const {currentRecord} = scriptContext;

   // get the approval status of the PO. 2 = Approved
   const approvalStatus = currentRecord.getValue({fieldId: 'approvalstatus'})

   // if the approval status is 2, then the PO is approved and the line cannot be deleted
   if (approvalStatus === '2') {
     alert("validateDelete: cannot delete the current line");
     return false;
   }

   // if the approval status is not 2, then the PO is not approved and the line can be deleted
   return true;
 }

 return {
   validateDelete: validateDelete
 };
});