code: func (c *Client) TorrentSet(payload *TorrentSetPayload) (err error) {
  	// Validate
  	if payload == nil {
  		return errors.New("payload can't be nil")
  	}
  	if len(payload.IDs) == 0 {
  		return errors.New("there must be at least one ID")
  	}
  	// Send payload
  	if err = c.rpcCall("torrent-set", payload, nil); err != nil {
  		err = fmt.Errorf("'torrent-set' rpc method failed: %v", err)
  	}
  	return
  }
docs: /*
  	Torrent Mutators
  	https://github.com/transmission/transmission/blob/2.9x/extras/rpc-spec.txt#L105
  */
  // TorrentSet apply a list of mutator(s) to a list of torrent ids.
  // https://github.com/transmission/transmission/blob/2.9x/extras/rpc-spec.txt#L107