code: function GetBlockTxnPacket(request) {
    if (!(this instanceof GetBlockTxnPacket))
      return new GetBlockTxnPacket(request);
  
    Packet.call(this);
  
    this.request = request || new bip152.TXRequest();
  }
docs: Represents a `getblocktxn` packet.
  @constructor
  @param {TXRequest?} request
  @property {TXRequest} request