code: def read_cBpack(filename):
      with gzip.open(filename, 'rb') as infile:
          data = msgpack.load(infile, raw=False)
      header = data[0]
      if (
          not isinstance(header, dict) or header.get('format') != 'cB'
          or header.get('version') != 1
      ):
          raise ValueError("Unexpected header: %r" % header)
      return data[1:]