docs: def on_canvas_slave__route_electrode_added(self, slave, electrode_id):
          '''
          .. versionchanged:: 0.11
              Draw temporary route currently being formed.
  
          .. versionchanged:: 0.11.3
              Update routes table by setting ``df_routes`` property of
              :attr:`canvas_slave`.
          '''
          logger.debug('Route electrode added: %s', electrode_id)
          if slave._route.electrode_ids is None:
              return
          df_route = pd.DataFrame([[-1, e, i] for i, e in
                                   enumerate(slave._route.electrode_ids)],
                                  columns=['route_i', 'electrode_i',
                                           'transition_i'])
          # XXX Negative `route_i` corresponds to temporary route being
          # drawn.  Append row entries for temporary route to existing routes
          # table.
          df_routes = slave.df_routes.loc[slave.df_routes.route_i >= 0].copy()
          self.canvas_slave.df_routes = pd.concat([df_routes, df_route])