code: def onLeftClickLabel(self, event):
          
          if event.Col == -1 and event.Row == -1:
              pass
          if event.Row < 0:
              if self.remove_cols_mode:
                  self.remove_col_label(event)
              else:
                  self.drop_down_menu.on_label_click(event)
          else:
              if event.Col < 0  and self.grid_type != 'age':
                  self.onSelectRow(event)
docs: 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).