Return cloudmask as a shapely geometry.

def cloudmask(self):
        """Return cloudmask as a shapely geometry."""
        polys = list(self._get_mask(mask_type="MSK_CLOUDS"))
        return MultiPolygon([
            poly["geometry"]
            for poly in polys
            if poly["attributes"]["maskType"] == "OPAQUE"
        ]).buffer(0)