List<@Nullable String> list = new ArrayList<>();
                for (String element : elements) {
                  list.add((element == null) ? null : "q" + element);
                }
                return Collections2.transform(
                    list, from -> isNullOrEmpty(from) ? null : from.substring(1));
              }
            })
        .named("Collections2.transform")
        .withFeatures(

  }

  /*
   * All the ContiguousSet generators below manually reject nulls here. In principle, we'd like to
   * defer that to Range, since it's ContiguousSet.create() that's used to create the sets. However,
   * that gets messy here, and we already have null tests for Range.
   */

  /*
   * These generators also rely on consecutive integer inputs (not necessarily in order, but no

    static FactoryMethodReturnsNullButNotAnnotated returnsNull() {
      return null;
    }
  }

  static class FactoryMethodReturnsNullAndAnnotated {
    private FactoryMethodReturnsNullAndAnnotated() {}

    public static @Nullable FactoryMethodReturnsNullAndAnnotated returnsNull() {
      return null;
    }
  }

  static class FactoryMethodAcceptsNull {

  protected final void afterDone() {
    super.afterDone();

    @RetainedLocalRef ImmutableCollection<? extends Future<?>> localFutures = futures;
    releaseResources(OUTPUT_FUTURE_DONE); // nulls out `futures`

    if (isCancelled() & localFutures != null) {
      boolean wasInterrupted = wasInterrupted();
      for (Future<?> future : localFutures) {
        future.cancel(wasInterrupted);
      }
    }
    /*

  @GwtIncompatible // suite
  @AndroidIncompatible // test-suite builders
  public static Test suite() {
    TestSuite suite = new TestSuite();
    // TODO(lowasser): should we force TreeMultimap to be more thorough about checking nulls?
    suite.addTest(
        SortedSetMultimapTestSuiteBuilder.using(
                new TestStringSetMultimapGenerator() {
                  @Override

  }

  /*
   * We don't permit nulls, but we wrap every comparator with nullsFirst().
   * Why? We want for queries like containsKey(null) to return false, but the
   * GWT SortedMap implementation that we delegate to throws
   * NullPointerException if the comparator does. Since our construction
   * methods ensure that null is never present in the map, it's OK for the

    if (delegate != null) {
      metadata =
          Ints.constrainToRange(size(), CompactHashing.DEFAULT_SIZE, CompactHashing.MAX_SIZE);
      delegate.clear(); // invalidate any iterators left over!
      table = null;
      size = 0;
    } else {
      Arrays.fill(requireKeys(), 0, size, null);
      Arrays.fill(requireValues(), 0, size, null);
      CompactHashing.tableClear(requireTable());

    TreeSet<Integer> set = Sets.newTreeSet(SOME_COLLECTION);
    verifySortedSetContents(set, SOME_COLLECTION, null);
  }

  public void testNewTreeSetFromIterable() {
    TreeSet<Integer> set = Sets.newTreeSet(SOME_ITERABLE);
    verifySortedSetContents(set, SOME_ITERABLE, null);
  }

  public void testNewTreeSetFromIterableDerived() {

    if (delegate != null) {
      metadata =
          Ints.constrainToRange(size(), CompactHashing.DEFAULT_SIZE, CompactHashing.MAX_SIZE);
      delegate.clear(); // invalidate any iterators left over!
      table = null;
      size = 0;
    } else {
      Arrays.fill(requireKeys(), 0, size, null);
      Arrays.fill(requireValues(), 0, size, null);
      CompactHashing.tableClear(requireTable());

    List<@Nullable String> list = newArrayList("a", null, "b", null, "a", null);
    assertEquals(2, frequency(list.iterator(), "a"));
    assertEquals(1, frequency(list.iterator(), "b"));
    assertEquals(0, frequency(list.iterator(), "c"));
    assertEquals(0, frequency(list.iterator(), 4.2));
    assertEquals(3, frequency(list.iterator(), null));
  }

  @GwtIncompatible // slow (~4s)