Writing XML Object to a File

Hi, I am using InDesign JavaScript to make an XML object in memory. When my script is done, I want to write the XML to a file. When I run the code below, the file is created, but the XML is not written to the file. Any help would be appreciated. Thanks. Rick

#target indesign
var partsMap = <partsMap />;
savePartsMap (partsMap);
function savePartsMap (partsMap) {
    
    var partsFile;
    
    // Make a File object for the parts map XML file.
    partsFile = new File("E:\\Test.xml");
    // Open the map file.
    partsFile.open("w");
    partsFile.write(partsMap);
    partsFile.close();
}