def _on_add_subset(self, message):
        self.invalidate()
        idx = self.subsets_index(1 - len(self.data_collection.subset_groups))
        self.new_item.emit(idx)
dataset/ETHPy150Open glue-viz/glue/glue/core/qt/data_collection_model.py/DataCollectionModel._on_add_subset/swapped operands of `-`