According to the documentation here:

I should be able to use an indicator (I'm trying to get the RSI for the forex universe) in the __init__ function of a class outside of the main class entry point. This didn't seem possible to me and it seems it isn't possible. When I try to call RSI in this outside class it is undefined. Can anyone enlighten me on what the documentation is showing with regard to how you create this "SelectionData" class?