MyCustomNode sample not working

Hello, I'm trying to implement the code from the sample "Custom Elements" (An example on how to extend certain DAZ Studio elements such as a DzNode or a DzModifier and save data custom to the implementation.).
It should be fairly simple, I just added a MyCustomNode with a custom element, but as I save the scene I get the error attached. I don't know what could be wrong, the implementation seems to be straightforward. Any idea? Thanks


sshot-69.jpg
3840 x 2160 - 408K