Given a dataset object and data in the appropriate format for
        the interface, return a simple scalar.

def unpack_scalar(cls, dataset, data):
        """
        Given a dataset object and data in the appropriate format for
        the interface, return a simple scalar.
        """
        if len(data) != 1:
            return data
        key = list(data.keys())[0]

        if len(data[key]) == 1 and key in dataset.vdims:
            scalar = data[key][0]
            return scalar.compute() if hasattr(scalar, 'compute') else scalar
        return data