def unpack_scalar(cls, dataset, data):
        """
        Given a dataset object and data in the appropriate format for
        the interface, return a simple scalar.
        """
        import dask.dataframe as dd
        if len(data.columns) > 1 or len(data) != 1:
            return data
        if isinstance(data, dd.DataFrame):
            data = data.compute()
        return data.iat[0,0]
Given a dataset object and data in the appropriate format for
        the interface, return a simple scalar.