Multiindex with single level no longer allows selecting columns

Multiindex with single level no longer allows selecting columns: a task in MiMo-V2.6-RL-harbor-code: MiMo-V2.6-RL Code (Harbor) (Harbor dataset). I have some old code that accidentally created a MultiIndex with a single level instead of a regular index, but everything worked fine with pandas…

The task

I have some old code that accidentally created a MultiIndex with a single level instead of a regular index, but everything worked fine with pandas 0.22.0. However, in new versions of pandas, that MultiIndex breaks pandas ability to select columns and gives an extremely misleading error message. In this case, I don't…

Part of FineEnvs/MiMo-V2.6-RL-harbor-code.