code: function MerkleblockMessage(arg, options) {
    Message.call(this, options);
    this.MerkleBlock = options.MerkleBlock; // constructor
    this.command = 'merkleblock';
    $.checkArgument(
      _.isUndefined(arg) || arg instanceof this.MerkleBlock,
      'An instance of MerkleBlock or undefined is expected'
    );
    this.merkleBlock = arg;
  }
docs: Contains information about a MerkleBlock
  @see https://en.bitcoin.it/wiki/Protocol_documentation
  @param {MerkleBlock} arg - An instance of MerkleBlock
  @param {Object=} options
  @param {Function} options.MerkleBlock - a MerkleBlock constructor
  @extends Message
  @constructor