def interaction_columns_used(self):
        return list(tz.unique(tz.concat(
            m.interaction_columns_used() for m in self.models.values())))
Columns from the interaction dataset used for filtering and in
dataset/ETHPy150Open UDST/urbansim/urbansim/models/dcm.py/MNLDiscreteChoiceModelGroup.interaction_columns_used