Better validation of scenario_params file
Currently when loading the scenario params CSV file there is very little validation performed. I think we check for a scenario_idx column but that's it. There also needs to be an n_replicates column (or at least a warning if it's missing) and at least one column of parameter values.
Furthermore, when loading a preprocessing or training config, we need to check the learned_params
section against the scenario params file and make sure all of the parameter names in learned_params
are actually correct as reflected by scenario params.
This came up also in #29, and in !74 (merged).