code: function(newVal, oldVal, batchNum) {
  		this.value = newVal;
  		var observation = this.observation;
  		if (observation) {
  			// it's possible the observation doesn't actually
  			// have any dependencies
  			if (observation.hasOwnProperty("_value")) {// can-observation 4.1+
  				observation._value = newVal;
  			} else {// can-observation < 4.1
  				observation.value = newVal;
  			}
  		}
  		updateOnChange(this, newVal, oldVal, batchNum);
  	}
docs: ## updater Updates the cached value and fires an event if the value has changed.