def all_same_area(self):
        """All contained data arrays are on the same area."""
        all_areas = [x.attrs.get('area', None) for x in self.values()]
        all_areas = [x for x in all_areas if x is not None]
        return all(all_areas[0] == x for x in all_areas[1:])
All contained data arrays are on the same area.