@total_ordering : Is it required

[sinhaharsh]

While this decorator makes it easy to create well behaved totally ordered types, it does come at the cost of slower execution and more complex stack traces for the derived comparison methods. If performance benchmarking indicates this is a bottleneck for a given application, implementing all six rich comparison methods instead is likely to provide an easy speed boost.

[sinhaharsh]

I didn't know this decorator has performance issues. I used it so I could use sorted()
Using sorted() helps me generate reports in a reproducible way, ensuring that modalities/sessions are not shuffled everytime. I will add it as a github issue

[sinhaharsh]

let’s review it later, and consider potential alternatives for future..
one could be :
self._sub_nodes = OrderedDict()

[sinhaharsh]

also reviewing the need for sorting in the first place.