Ah memories... I once had 100K Python 2.x codebase to maintain. No docs, no tests and then being required to add features. Had to use the debugger[1] to make sense of the codebase and types, formats etc. Sheer madness and such a waste of time...

To this day, I'm baffled by the dynamic language folks who cannot get their head around how strictness/rigor (via a good expressive type system) actually makes maintenance easier and more importantly: cheaper.

[1] https://github.com/inducer/pudb