code: function() {
  		if (this._bindingState.parent === false && this._parentToChild === true) {
  			var options = this._options;
  			this._bindingState.parent = true;
  			turnOnListeningAndUpdate(options.parent, options.child, this._updateChild, options.queue);
  		}
  	}
docs: Listen for changes to the parent observable and update the child