def onLeftClickLabel(self, event):
        """
        When user clicks on a grid label, determine if it is a row label or a col label.
        Pass along the event to the appropriate function.
        (It will either highlight a column for editing all values, or highlight a row for deletion).
        """
        if event.Col == -1 and event.Row == -1:
            pass
        elif event.Col < 0:
            self.onSelectRow(event)
        elif event.Row < 0:
            self.drop_down_menu.on_label_click(event)