public SessionsPage(Speaker speaker)
        {
            var sessions = Repository.GetSessions ().Where(x => x.SpeakerName == speaker.Name).ToList();
            this.BindingContext = sessions;

            Initialize (sessions);
        }
        public SpeakerDetailPage(Speaker speaker)
        {
            this.BindingContext = speaker;
            InitializeComponent ();

            showSessions.Clicked += async (sender, e) => {
                await this.Navigation.PushAsync(new SessionsPage(speaker));
            };
        }