def _emit_select(self, cluster_ids, **kwargs):
        """Choose spikes from the specified clusters and emit the
        `select` event on the GUI."""
        # Remove non-existing clusters from the selection.
        cluster_ids = self._keep_existing_clusters(cluster_ids)
        logger.debug("Select cluster(s): %s.",
                     ', '.join(map(str, cluster_ids)))
        self.emit('select', cluster_ids, **kwargs)
Choose spikes from the specified clusters and emit the
        `select` event on the GUI.