private void OnTaskListDeleted(object sender, TaskListViewModel taskListVm)
        {
            if (!TaskListsViewModels.Contains(taskListVm))
            {
                return;
            }

            TaskListsViewModels.Remove(taskListVm);
            TaskListsChanged?.Invoke(this, EventArgs.Empty);
        }
 private void OnNewTaskListAdded(object sender, TaskList taskList)
 {
     TaskListsViewModels.Add(GetTaskListVm(taskList));
     TaskListsChanged?.Invoke(this, EventArgs.Empty); // have to invoke this event here for the view to update
 }