Question about line in paper

[Sreyan88]

Hi there, great paper! I had a question regarding this line in the paper:

Locations of such intermediate layers are dynamically drawn from a given discrete probability distribution at each training epoch.

I am a bit confused, how do you actually find out which intermediate layers to add auxiliary classifiers to? I also don't see a code snippet for that, I only see auxiliary classifiers from head_3 and head_4 hardcoded. Can you please help understand this line?

Thank You again!