@staticmethod
def _get_map_cls(map_type):
    """Get map class for given `map_type` string.

        This should probably be a registry dict so that users
        can add supported map types to the `gammapy.maps` I/O
        (see e.g. the Astropy table format I/O registry),
        but that's non-trivial to implement without avoiding circular imports.
        """
    if map_type == 'wcs':
        from .wcsnd import WcsNDMap
        return WcsNDMap
    elif map_type == 'wcs-sparse':
        raise NotImplementedError()
    elif map_type == 'hpx':
        from .hpxnd import HpxNDMap
        return HpxNDMap
    elif map_type == 'hpx-sparse':
        raise NotImplementedError()
    elif map_type == 'region':
        from .regionnd import RegionNDMap
        return RegionNDMap
    else:
        raise ValueError(f'Unrecognized map type: {map_type!r}')
