Push Notification Plugin for Xamarin on receiving message

I have integrated push notification on Xamarin.Forms by using this plugin: https://github.com/rdelrosario/xamarin-plugins/tree/master/PushNotification using our own web service on Rails.

What I need to do is to place the returned message properly in the notification. It currently is empty when it arrives.
The object returned is (default values from the documentation):

{
    "key": "value",
    "key2": "[\"array\",\"value\"]",
    "collapse_key": "do_not_collapse"
}

I reckon, this is where I format the message, but how do I do it?

void IPushNotificationListener.OnMessage(JObject arameters, DeviceType deviceType)
{
     Debug.WriteLine("Message Arrived");
}