private void addDottedArrow(int nodeIndex, boolean isUp) {
   myModification.createEdge(
       new GraphEdge(nodeIndex, null, null, isUp ? DOTTED_ARROW_UP : DOTTED_ARROW_DOWN));
 }
 private void addDottedEdge(int nodeIndex1, int nodeIndex2) {
   myModification.createEdge(new GraphEdge(nodeIndex1, nodeIndex2, null, DOTTED));
 }