code: function Inventory(obj) {
    this.type = obj.type;
    if (!BufferUtil.isBuffer(obj.hash)) {
      throw new TypeError('Unexpected hash, expected to be a buffer');
    }
    this.hash = obj.hash;
  }
docs: A constructor for inventory related Bitcoin messages such as
  "getdata", "inv" and "notfound".
  @param {Object} obj
  @param {Number} obj.type - Inventory.TYPE
  @param {Buffer} obj.hash - The hash for the inventory
  @constructor