code: protected void fireKNNsInserted(DBIDs insertions, DBIDs updates) {
      KNNChangeEvent e = new KNNChangeEvent(this, KNNChangeEvent.Type.INSERT, insertions, updates);
      Object[] listeners = listenerList.getListenerList();
      for(int i = listeners.length - 2; i >= 0; i -= 2) {
        if(listeners[i] == KNNListener.class) {
          ((KNNListener) listeners[i + 1]).kNNsChanged(e);
        }
      }
    }
docs: Informs all registered KNNListener that new kNNs have been inserted and as
  a result some kNNs have been changed.
  
  @param insertions the ids of the newly inserted kNNs
  @param updates the ids of kNNs which have been changed due to the
  insertions
  @see KNNListener