public MainViewModel(IFeedPreviewsLoader feedPreviews)
        {
            _feedPreviews = feedPreviews;

			AddSubscriptionCommand = NavigateCommand.WithParameter(() => Locator.Current.GetService<AddSubscriptionViewModel>());
			Feeds = feedPreviews.CreateCollection().CreateDerivedCollection(f => f, null, FreshFirstOrderer);

            this.WhenActivated(d => feedPreviews.Load());
        }