code: function (key, defaultValue) {
              var input = self.session.get('_old_input', []);
  
              // Input that is flashed to the session can be easily retrieved by the
              // developer, making repopulating old forms and the like much more
              // convenient, since the request's previous input is available.
              if (key) {
                  return isset(input[key]) ? input[key] : defaultValue;
              } else {
                  return input;
              }
          }
docs: Retrieve an old input item.
  
  @param  {String} key
  @param  {*} defaultValue
  @return {*}