code: def split(self, spike_ids=None, spike_clusters_rel=0):
          
          if spike_ids is None:
              spike_ids = self.emit('request_split', single=True)
              spike_ids = np.asarray(spike_ids, dtype=np.int64)
              assert spike_ids.dtype == np.int64
              assert spike_ids.ndim == 1
          if len(spike_ids) == 0:
              msg = ("You first need to select spikes in the feature "
                     "view with a few Ctrl+Click around the spikes "
                     "that you want to split.")
              self.emit('error', msg)
              return
          self.clustering.split(spike_ids,
                                spike_clusters_rel=spike_clusters_rel)
          self._global_history.action(self.clustering)
docs: Split the selected spikes.