def _comparable(self):
        """Get a comparable version of the DatasetID.

        Without this DatasetIDs often raise an exception when compared in
        Python 3 due to None not being comparable with other types.
        """
        return self._replace(
            name='' if self.name is None else self.name,
            wavelength=tuple() if self.wavelength is None else self.wavelength,
            resolution=0 if self.resolution is None else self.resolution,
            polarization='' if self.polarization is None else self.polarization,
            calibration='' if self.calibration is None else self.calibration,
        )
Get a comparable version of the DatasetID.

        Without this DatasetIDs often raise an exception when compared in
        Python 3 due to None not being comparable with other types.