code: def rereference(self):
          
          selectedItems = self.idx_l0.selectedItems()
  
          chan_to_plot = []
          for selected in selectedItems:
              chan_to_plot.append(selected.text())
          self.highlight_channels(self.idx_l1, chan_to_plot)
docs: Automatically highlight channels to use as reference, based on
          selected channels.