How to use the hub.bbox.Bbox function in hub

def _download_chunk(self, cloudpath):

        chunk = self._storage.get_or_none(cloudpath)
        if chunk:
            chunk = self._codec.decode(chunk)
        else:
            chunk = np.zeros(shape=self.chunk, dtype=self.dtype)

        bbox = Bbox.from_filename(cloudpath)
        return chunk, bbox

def _chunkify(self, cloudpaths, requested_bbox, item):
        chunks = []
        for path in cloudpaths:
            cloudchunk = Bbox.from_filename(path)
            intersection = Bbox.intersection(cloudchunk, requested_bbox)
            chunk_slices = (intersection - cloudchunk.minpt).to_slices()
            item_slices = (intersection - requested_bbox.minpt).to_slices()

            chunk = None
            if np.any(np.array(intersection.to_shape()) != np.array(self.chunk)):
                chunk, _ = self._download_chunk(path)
            else:
                chunk = np.zeros(shape=self.chunk, dtype=self.dtype)

            chunk.setflags(write=1)
            chunk[chunk_slices] = item[item_slices]
            chunks.append(chunk)

        return zip(cloudpaths, chunks)