code: private String extractStringValue(XMLObject xmlo) {
          if (xmlo instanceof XSString) {
              return ((XSString)xmlo).getValue();
          } else if (xmlo instanceof XSAnyImpl) {
              return ((XSAnyImpl)xmlo).getTextContent();
          }
          logger.warn("Unable to map attribute class {} to String. Unknown type. Enable TRACE logging to see attribute name",
                  xmlo.getClass());
          return null;
      }
docs: Extracts the string value of the XMLObject depending upon its type.
  @param xmlo XMLObject
  @return String value of object. Null if unable to convert object to string.