code: private static Collection<String> getStringValues(final List<?> items) {
          val list = new ArrayList<String>();
          items.forEach(d -> {
              if (d instanceof XSURI) {
                  list.add(((XSURI) d).getValue());
              } else if (d instanceof XSString) {
                  list.add(((XSString) d).getValue());
              }
          });
          return list;
      }
docs: Gets string values from the list of mdui objects.
  
  @param items the items
  @return the string values