assertEquals(ImmutableSortedSet.of(4, 6, 8, 10), Sets.subSet(set, Range.atLeast(4)));
    assertEquals(ImmutableSortedSet.of(8, 10), Sets.subSet(set, Range.atLeast(7)));
    assertEquals(empty, Sets.subSet(set, Range.atLeast(20)));

    assertEquals(set, Sets.subSet(set, Range.greaterThan(0)));
    assertEquals(ImmutableSortedSet.of(6, 8, 10), Sets.subSet(set, Range.greaterThan(4)));

  }

  @Override
  public NavigableSet<E> subSet(
      E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
    return new SafeTreeSet<>(
        delegate.subSet(
            checkValid(fromElement), fromInclusive, checkValid(toElement), toInclusive));
  }

  @Override
  public SortedSet<E> subSet(E fromElement, E toElement) {
    return subSet(fromElement, true, toElement, false);
  }

    assertTrue(
        "containsAll(empty) should return true", collection.containsAll(MinimalCollection.of()));
  }

  @CollectionSize.Require(absent = ZERO)
  public void testContainsAll_subset() {
    assertTrue(
        "containsAll(subset) should return true",
        collection.containsAll(MinimalCollection.of(e0())));
  }

  public void testContainsAll_sameElements() {
    assertTrue(

  }

  /**
   * {@inheritDoc}
   *
   * <p>This method returns a serializable {@code ImmutableSortedSet}.
   *
   * <p>The {@link SortedSet#subSet} documentation states that a subset of a subset throws an {@link
   * IllegalArgumentException} if passed a {@code fromElement} smaller than an earlier {@code
   * fromElement}. However, this method doesn't throw an exception in that situation, but instead

  public void testRetainAll_supersetUnsupported() {
    expectReturnsFalseOrThrows(superset);
    expectUnchanged();
  }

  // retainAll(subset)

  @CollectionFeature.Require(SUPPORTS_REMOVE)
  @CollectionSize.Require(absent = {ZERO, ONE})
  public void testRetainAll_subset() {
    expectReturnsTrue(nonEmptyProperSubset);
    expectContents(nonEmptyProperSubset.toRetain);
  }

   * have started execution. This applies also to tasks given to {@code invokeAll} or {@code
   * invokeAny} which are pending serial execution, even the subset of the tasks that have not yet
   * started execution. It is unclear from the {@code ExecutorService} specification if these should
   * be included, and it's much easier to implement the interpretation that they not be. Finally, a

 *
 * @author Hayward Chan
 */
@ElementTypesAreNonnullByDefault
final class RegularImmutableSortedSet<E> extends ImmutableSortedSet<E> {

  /** true if this set is a subset of another immutable sorted set. */
  final boolean isSubset;

  private @Nullable Comparator<E> unusedComparatorForSerialization;
  private @Nullable E unusedElementForSerialization;

[Java style guide]: https://google.github.io/styleguide/javaguide.html
[well-formed commit message]: https://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html

#### Merging pull requests ####

Due to Guava's nature as a subset of Google's internal codebase which is
automatically synced to the public GitHub repository, we are unable to merge
pull requests directly into the master branch. Instead, once a pull request is

    assertEquals(Sets.<@Nullable String>newHashSet(null, "tree"), keySet.headSet("yahoo"));
    assertEquals(Sets.newHashSet("google"), keySet.tailSet("yahoo"));
    assertEquals(Sets.newHashSet("tree"), keySet.subSet("ask", "yahoo"));
  }

  @GwtIncompatible // SerializableTester
  public void testExplicitComparatorSerialization() {
    TreeMultimap<@Nullable String, @Nullable Integer> multimap = createPopulate();

            3),
        rangeMap.asMapOfRanges());

    assertThrows(IllegalArgumentException.class, () -> sub.put(Range.open(9, 12), 5));

    RangeMap<Integer, Integer> subSub = sub.subRangeMap(Range.closedOpen(5, 5));
    subSub.put(Range.closedOpen(5, 5), 6); // should be a no-op
    assertEquals(
        ImmutableMap.of(
            Range.open(3, 7),
            1,
            Range.closed(7, 9),