Constructor a transaction object.

@param {Object} config Configuration options.
@param {ContractInstance} config.parent The parent `ContratInstance`.
@param {String} config.hash Transaction hash.
function Transaction(config) {
      _classCallCheck(this, Transaction);

      this._web3 = config.parent._web3;
      this._logger = config.parent._logger;
      this._hash = config.hash;
    }