Python behave: get list of selected features in before_all

Question

For a pre-processing (cross-cutting) task, I would like to obtain a list of all selected "Features" already in the before_all hook. However, I only get very basic data via the Context there, like "Context.config". Where, as far as I can see, only an in-memory representation of the run configuration (command line parameters) is accessible.

I mean, behave must have such a list eventually since this is what it processes. How can I access it?

Background: I want to extract some data out of all selected Features and perform a central, expensive pre-processing in the before_all hook.