IntSet () { IntSet collapsedMerges = new IntOpenHashSet(); for (int i = myLinearBekGraph.myGraph.nodesCount() - 1; i >= 0; i--) { MergeFragment fragment = getFragment(i); if (fragment != null) { fragment.collapse(myLinearBekGraph); collapsedMerges.add(fragment.getParent()); } } return collapsedMerges; }