@Override
 public W get(String key) throws NoSuchEntryException {
   try {
     return provider.get(key, content);
   } catch (NoSuchCollectionException e) {
     throw new NoSuchEntryException(e);
   }
 }
 @Override
 public Iterator<String> keys() {
   return provider.keys(content);
 }
 @Override
 public Iterator<W> iterator() {
   return (Iterator<W>) provider.values(content);
 }