private static void StartDocument(XmlTextWriter w)
 {
     w.WriteStartDocument();
     w.WriteStartElement("MzIdentML");
     w.WriteAttribute("id", 1);
     w.WriteAttribute("version", "1.1.0");
     w.WriteAttribute("xmlns", "http://psidev.info/psi/pi/mzIdentML/1.1");
     w.WriteAttribute("xmlns:xsi", "http://www.w3.org/2001/XMLSchema-instance");
     w.WriteAttribute("xsi:schemaLocation", "http://www.psidev.info/files/mzIdentML1.1.0.xsd");
     w.WriteAttributeFormat("creationDate", "{0:s}", DateTime.Now);
 }