code: def pick_event_handler(self, event):
          
          info = {'options': self.get_available_channels(),
                  'guiEvent': event.mouseevent.guiEvent,
                  }
  
          if hasattr(self, 'xlabel_artist') and (event.artist == self.xlabel_artist):
              info['axis_num'] = 0
              self.callback(Event('axis_click', info))
  
          if hasattr(self, 'ylabel_artist') and (event.artist == self.ylabel_artist):
              info['axis_num'] = 1
              self.callback(Event('axis_click', info))
docs: Handles pick events