code: public void defineProperty(Symbol key, Object value,
                                 int attributes)
      {
          checkNotSealed(key, 0);
          put(key, this, value);
          setAttributes(key, attributes);
      }
docs: A version of defineProperty that uses a Symbol key.
  @param key symbol of the property to define.
  @param value the initial value of the property
  @param attributes the attributes of the JavaScript property