private void CleanupViewModel(object context)
        {
            VstoContribLog.Debug(_ => _("Cleaning up viewmodel for context: {0}", context.ToLogFormat()));
            if (!contextToViewModelLookup.ContainsKey(context))
            {
                VstoContribLog.Warn(_ => _("Cannot find ViewModel to cleanup: {0}", context.ToLogFormat()));
                return;
            }

            var viewModelInstance = contextToViewModelLookup[context];

            VstoContribLog.Info(_ => _("ViewModel is {0}", viewModelInstance.ToLogFormat()));

            var notifyOfPropertyChanged = viewModelInstance as INotifyPropertyChanged;

            if (notifyOfPropertyChanged != null)
            {
                notifyOfPropertyChanged.PropertyChanged -= NotifiesOfPropertyChangedPropertyChanged;
            }

            viewModelInstance.Cleanup();
            vstoContribContext.ViewModelFactory.Release(viewModelInstance);
            customTaskPaneRegister.CleanupViewModel(viewModelInstance);
            contextToViewModelLookup.Remove(context);
        }