code: def __realized_bbox(self, requested_bbox):
      
      realized_bbox = requested_bbox.expand_to_chunk_size(self.underlying, offset=self.voxel_offset)
      return Bbox.clamp(realized_bbox, self.bounds)
docs: The requested bbox might not be aligned to the underlying chunk grid 
      or even outside the bounds of the dataset. Convert the request into
      a bbox representing something that can be actually downloaded.
  
      Returns: Bbox