code: def add_electrode(self, electrode, label=None):
          
          if not label:
              label = "Electrode {}".format(len(self._electrodes) + 1)
          self._electrodes[label] = electrode
docs: Add an electrode to the plot.
  
          Args:
              electrode: An electrode. All electrodes satisfying the
                  AbstractElectrode interface should work.
              label: A label for the electrode. If None, defaults to a counting
                  system, i.e. 'Electrode 1', 'Electrode 2', ...