Make node trees attached to objects

I am working on a implicit geometry node system. I cannot figure out how to attach the Node Tree to object. If it isn’t clear what i want, I want to be able to have multiple node networks for every object Ideally the same as the material system does this.
I have taken a look at Blend Lux Core way of solving this issue but again i cannot really make it work since they are using their own implementation of the Node Tree class.
If you need to take a look at how i am implementing the base Node Tree and Nodes: