@Override
    public @NotNull Iterator<LookupElement> iterator() {
      Set<LookupElement> processed = new ReferenceOpenHashSet<>(mySrcSet.size());
      Set<Collection<LookupElement>> arraysProcessed = new ReferenceOpenHashSet<>();

      final Iterable<? extends LookupElement> next = myNext == null ? mySource : myNext.classify(mySource, myContext);
      Iterator<LookupElement> base = FilteringIterator.create(next.iterator(), processed::add);
      return new FlatteningIterator<>(base) {
        @Override
        protected @NotNull Iterator<LookupElement> createValueIterator(LookupElement element) {
          List<LookupElement> toLift;
          synchronized (LiftShorterItemsClassifier.this) {
            toLift = new ArrayList<>(myToLift.get(element));
          }
          List<LookupElement> shorter = addShorterElements(toLift);
          List<LookupElement> singleton = Collections.singletonList(element);
          if (shorter != null) {
            if (myLifted != null) {
              myLifted.addAll(shorter);
            }
            Iterable<LookupElement> lifted = myNext == null ? shorter : myNext.classify(shorter, myContext);
            return (myLiftBefore ? ContainerUtil.concat(lifted, singleton) : ContainerUtil.concat(singleton, lifted)).iterator();
          }
          return singleton.iterator();
        }

        private @Nullable List<LookupElement> addShorterElements(@Nullable Collection<LookupElement> from) {
          List<LookupElement> toLift = null;
          if (from == null) {
            return null;
          }

          if (arraysProcessed.add(from)) {
            for (LookupElement shorterElement : from) {
              if (mySrcSet.contains(shorterElement) && processed.add(shorterElement)) {
                if (toLift == null) {
                  toLift = new ArrayList<>();
                }
                toLift.add(shorterElement);
              }
            }
          }
          return toLift;
        }
      };
    }
@Override
    public @NotNull Iterator<LookupElement> iterator()