@Override
  public void merge(@NotNull PomChangeSet next) {
    for (TreeChangeImpl change : ((TreeChangeEventImpl)next).myChangedElements.values()) {
      TreeChangeImpl existing = myChangedElements.get(change.getChangedParent());
      if (existing != null) {
        existing.appendChanges(change);
      }
      else if (!integrateIntoExistingChanges(change.getChangedParent())) {
        mergeChange(change);
      }
    }
  }
@Override
  public void merge(@NotNull PomChangeSet next)