GetMainPage command obsolete in Xamarin.Forms Sample

I am working through the Xamarin.Forms Heart Rate Monitor Sample code. on the mainActivity.cs in .Droid, the following error is flagged up over the LoadApplication (new App ()); line.
Error:
/Users/georgeedwards/Downloads/xamarin-forms-samples-master/BluetoothHeartRateMonitor/HeartRateMonitor.Droid/MainActivity.cs(4,4): Warning CS0618:Xamarin.Forms.Platform.Android.FormsApplicationActivity.SetPage(Xamarin.Forms.Page)' is obsolete: Please use protected LoadApplication (Application app) instead' (CS0618) (Gas-Sense.Droid)

The suggested replacement doesn't work, as app is an unexpected symbol. What should I put?