code: func checkDecodedChunkState(version Version, chunk []byte, seqno packetSeqno, isFinal bool) error {
  	// The first decoded block has seqno 1, since the header bytes
  	// are decoded first.
  	return checkChunkState(version, len(chunk), uint64(seqno-1), isFinal)
  }
docs: // checkDecodedChunkState sanity-checks some decoded chunk
  // parameters. A returned error means there's something wrong with the
  // decoded stream.