private Pair<SimpleModificationTracker, EventDispatcher<ModificationTrackerListener>> getFacetInfo(final Facet<?> facet) {
    Pair<SimpleModificationTracker, EventDispatcher<ModificationTrackerListener>> pair = myModificationsTrackers.get(facet);
    if (pair != null) {
      return pair;
    }

    myModificationsTrackers.putIfAbsent(facet, new Pair<>(new SimpleModificationTracker(), EventDispatcher.create(ModificationTrackerListener.class)));
    return myModificationsTrackers.get(facet);
  }
private Pair<SimpleModificationTracker, EventDispatcher<ModificationTrackerListener>> getFacetInfo(final Facet<?> facet)