@Override
 public <X> X unwrap(ContentType value, Class<X> type, WrapperOptions options) {
   if (value == null) {
     return null;
   }
   // TODO handle Enum ordinal?
   if (String.class.isAssignableFrom(type)) {
     return (X) value.toString();
   }
   throw unknownUnwrap(type);
 }
 @Override
 public String toString(ContentType value) {
   return value.toString();
 }