So I hacked something together, but I figured you could do it better :)
I put that in the panel init but that's not the right place for the call. This is sufficient to just respond to a mouse event (so that you could receive the nc.keys.MOUSE event)
To actually get the mouse, you need to call getmouse and expose the struct via the node interface.
What I ended up doing was creating a separate callback inputMouse. I don't think that's the right approach but at least it works :)