if the following are true:

• expression state at time 29 = "iterate_args"
• arguments stack at time 29 = [ [ locations, [ "ES", [ "Spain", [ ] ] ] ], [ ] ]
• parent stack at time 29 = [ __setitem__(locations, "ES", "Spain"), [ ] ]

then parent stack at time 30 = [ __setitem__(locations, "ES", "Spain"), [ ] ]

Start from the conclusion and work back up the proof. Click the arrow to show the parents.