code: func (t *Torrent) DownloadPieces(begin, end pieceIndex) {
  	t.cl.lock()
  	defer t.cl.unlock()
  	t.downloadPiecesLocked(begin, end)
  }
docs: // Raise the priorities of pieces in the range [begin, end) to at least Normal
  // priority. Piece indexes are not the same as bytes. Requires that the info
  // has been obtained, see Torrent.Info and Torrent.GotInfo.