code: def update_widget_channels(self):
          
          sel1 = self.x_axis_list.GetSelection()
          sel2 = self.y_axis_list.GetSelection()
  
          if sel1 >= 0 and sel2 >= 0:
              channel_1 = self.x_axis_list.GetString(sel1)
              channel_2 = self.y_axis_list.GetString(sel2)
              self.fcgatemanager.set_axes((channel_1, channel_2), self.ax)
docs: Parameters
          -------------
          axis : 'x' or 'y'
          event : pick of list text