code: public ReturnValueType<ConstructorType<T>> getOrCreateReturnValue()
     {
        Node node = childNode.getOrCreate("return-value");
        ReturnValueType<ConstructorType<T>> returnValue = new ReturnValueTypeImpl<ConstructorType<T>>(this, "return-value", childNode, node);
        return returnValue;
     }
docs: If not already created, a new <code>return-value</code> element with the given value will be created.
  Otherwise, the existing <code>return-value</code> element will be returned.
  @return  a new or existing instance of <code>ReturnValueType<ConstructorType<T>></code>