BrightIdeasSoftware.ObjectListView.UnsubscribeNotifications C# (CSharp) Method

        private void UnsubscribeNotifications(IEnumerable models)
        {
            if (models == null) {
                foreach (INotifyPropertyChanged notifier in this.subscribedModels.Keys) {
                    notifier.PropertyChanged -= HandleModelOnPropertyChanged;
                }
                subscribedModels = new Hashtable();
            } else {
                foreach (object x in models) {
                    INotifyPropertyChanged notifier = x as INotifyPropertyChanged;
                    if (notifier != null) {
                        notifier.PropertyChanged -= HandleModelOnPropertyChanged;
                        subscribedModels.Remove(notifier);
                    }
                }
            }
        }