code: function GetblocksMessage(arg, options) {
    Message.call(this, options);
    this.command = 'getblocks';
    this.version = options.protocolVersion;
    if (!arg) {
      arg = {};
    }
    arg = utils.sanitizeStartStop(arg);
    this.starts = arg.starts;
    this.stop = arg.stop;
  }
docs: Query another peer about blocks. It can query for multiple block hashes,
  and the response will contain all the chains of blocks starting from those
  hashes.
  @param {Object=} arg
  @param {Array=} arg.starts - Array of buffers or strings with the starting block hashes
  @param {Buffer=} arg.stop - Hash of the last block
  @param {Object} options
  @extends Message
  @constructor