code: function() {
  			canReflect.onValue( observation, updater,"notify");
  			if (observation.hasOwnProperty("_value")) {// can-observation 4.1+
  				compute.value = observation._value;
  			} else {// can-observation < 4.1
  				compute.value = observation.value;
  			}
  		}
docs: Call `onchanged` when any source observables change.