SortedSet<String> subset = elementSet.subSet("b", "f");
    assertThat(subset).containsExactly("b", "c", "d", "e").inOrder();

    assertTrue(subset.remove("c"));
    assertThat(elementSet).containsExactly("a", "b", "d", "e", "f").inOrder();
    assertThat(subset).containsExactly("b", "d", "e").inOrder();
    assertEquals(10, ms.size());

    assertFalse(subset.remove("a"));

    assertThat(set.subSet(1, 4)).containsExactly(1, 2, 3).inOrder();
    assertThat(set.subSet(2, 4)).containsExactly(2, 3).inOrder();
    assertThat(set.subSet(3, 4)).containsExactly(3).inOrder();
    assertThat(set.subSet(3, 3)).isEmpty();
    assertThat(set.subSet(2, 3)).containsExactly(2).inOrder();
    assertThat(set.subSet(1, 3)).containsExactly(1, 2).inOrder();

    assertThat(set.subSet(1, 4)).containsExactly(1, 2, 3).inOrder();
    assertThat(set.subSet(2, 4)).containsExactly(2, 3).inOrder();
    assertThat(set.subSet(3, 4)).containsExactly(3).inOrder();
    assertThat(set.subSet(3, 3)).isEmpty();
    assertThat(set.subSet(2, 3)).containsExactly(2).inOrder();
    assertThat(set.subSet(1, 3)).containsExactly(1, 2).inOrder();

  }

  @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);
  }

  }

  @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);
  }

                    set.addAll(difference);
                    Set<String> subset = newHashSet(samples());
                    subset.removeAll(difference);
                    return difference(set, subset);
                  }
                })
            .named("set - subset")
            .withFeatures(

         * greater than tooHigh.
         */
        return ContiguousSet.create(Range.openClosed(0, 1), DiscreteDomain.integers()).subSet(0, 1);
      }
      int tooHigh = set.last() + 1;
      int tooLow = set.first() - 1;
      set.add(tooHigh);
      set.add(tooLow);
      return checkedCreate(set).subSet(tooLow + 1, tooHigh);
    }
  }

  @GwtIncompatible // NavigableSet

  }

  /**
   * {@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

         * greater than tooHigh.
         */
        return ContiguousSet.create(Range.openClosed(0, 1), DiscreteDomain.integers()).subSet(0, 1);
      }
      int tooHigh = set.last() + 1;
      int tooLow = set.first() - 1;
      set.add(tooHigh);
      set.add(tooLow);
      return checkedCreate(set).subSet(tooLow + 1, tooHigh);
    }
  }

  @GwtIncompatible // NavigableSet

    }

    @Override
    public Comparator<? super E> comparator() {
      return multiset().comparator();
    }

    @Override
    public SortedSet<E> subSet(@ParametricNullness E fromElement, @ParametricNullness E toElement) {
      return multiset().subMultiset(fromElement, CLOSED, toElement, OPEN).elementSet();
    }

    @Override