code: function (filter, keys) {
              if (self.session) {
                  var flash = isset(filter) ? self.input[filter](keys) : self.input.all();
  
                  self.session.flash('_old_input', flash);
              }
          }
docs: Flash the input for the current request to the session.
  
  @param  {String} filter
  @param  {Object}  keys