code: def extract_metatile(io, fmt, offset=None):
      
  
      ext = fmt.extension
      if offset is None:
          tile_name = '0/0/0.%s' % ext
      else:
          tile_name = '%d/%d/%d.%s' % (offset.zoom, offset.column, offset.row,
                                       ext)
  
      with zipfile.ZipFile(io, mode='r') as zf:
          if tile_name in zf.namelist():
              return zf.read(tile_name)
          else:
              return None
docs: Extract the tile at the given offset (defaults to 0/0/0) and format from
      the metatile in the file-like object io.