I have implemented the classes you have and used the example xml you provided.
I created a main function to test
public static void main(String args[]) throws Exception {
Serializer serializer = new Persister(new Format("<?xml version=\"1.0\" encoding= \"UTF-8\" ?>"));
File source = new File("sample.xml");
Package p = serializer.read(Package.class, source);
System.out.println(p.name);
}
The output is
GO Sales (nalysis)
Inspecting the object p in debug mode shows it has the two Sets with two and three elements. Your code works fine for me.