Help with script to read specific XMP metadata in an image

I'm creating a script for Photoshop to read a specific XMP metadata field in the file info of an image. I'm trying to specifically read the data that is located under the <dc:subject> area. I want to access the data under dc: subject > rdf: Bag > rdf: li. Here's an example (as it would appear in Raw Data field under an image's file info):

<dc:subject>
    <rdf:Bag>
        <rdf:li>****DATA I NEED HERE****</rdf:li>
    </rdf:Bag>
</dc:subject>

So far, I have a script that can read XMP metadata, but I can't access that specific line of data I showed in the above example. I commented line 43 -- that needs to be updated so it can read into the dc: subject data. I can currently access certain pieces of data in an image file. For example, using this code, if i run xmp.getProperty(XMPConst.NS_DC, "subject") through the console, I get a result back, but it's not the data I need. I figured if I used the same logic as I applied to line 43, it would give me the results I am looking for. Any ideas on how to access the data I'm looking for?

function loadXMPLibrary() {
    if (!ExternalObject.AdobeXMPScript) {
        try {
            ExternalObject.AdobeXMPScript = new ExternalObject('lib:AdobeXMPScript');
        } catch (e) {
            alert("Can't load XMP Script Library")
            return false;
        }
    }
    return true;
}
function unloadXMPLibrary() {
    if (ExternalObject.AdobeXMPScript) {
        try {
            ExternalObject.AdobeXMPScript.unloadXMPLibrary();
            ExternalObject.AdobeXMPScript = undefined;
        } catch (e) {
            alert("Couldn't unload XMP Script Library")
        }
    }
}
function writeXMP(xmpData, xmpFile) {
    xmpFile.open('w', 'Text');
    xmpFile.encoding = 'UTF-8'
    xmpFile.write(xmpData)
    xmpFile.close()
}
function showXMPMetadata() {
    var xmpLoad = loadXMPLibrary();
    if (xmpLoad) {
        var filepath = app.activeDocument.path + '/' + app.activeDocument.name;
        var myFile = File(filepath);
        xmpFile = new XMPFile(myFile.fsName, XMPConst.UNKNOWN, XMPConst.OPEN_FOR_READ);
        xmp = xmpFile.getXMP();
        var myXmp = xmp.serialize();
        xmpFile.closeFile(XMPConst.CLOSE_UPDATE_SAFELY)
        var skus = myXmp.getProperty(XMPConst.NS_RDF,"Bag"); //this needs to be updated
        unloadXMPLibrary ();
        return skus;
    };
};