code: function() {
  
  		var new_value = this._evaluate(),
  			event_args;
  
  		if (new_value !== this._value) {
  
  			event_args = {old_value: this._value};
  			this._value = new_value;
  			this._fire('changed', event_args);
  
  		}
  
  	}
docs: Refresh `_value` and fire {@link Lava.scope.Argument#event:changed}
  @private