private var contextSwitchCount = 0

  /** Guarded by [TaskRunner.lock]. */
  private var activeThreads = 0

  /** A task runner that posts tasks to this fake. Tasks won't be executed until requested. */
  val taskRunner: TaskRunner =
    TaskRunner(
      object : TaskRunner.Backend {
        override fun execute(
          taskRunner: TaskRunner,
          runnable: Runnable,

    assertNull(map.get(null));
  }

  public void testAsMultimap() {
    ImmutableMap<String, Integer> map =
        ImmutableMap.of("one", 1, "won", 1, "two", 2, "too", 2, "three", 3);
    ImmutableSetMultimap<String, Integer> expected =
        ImmutableSetMultimap.of("one", 1, "won", 1, "two", 2, "too", 2, "three", 3);
    assertEquals(expected, map.asMultimap());
  }

  public void testAsMultimapWhenEmpty() {

   * HashMultimap#create()}, {@link LinkedHashMultimap#create()}, {@link
   * LinkedListMultimap#create()}, {@link TreeMultimap#create()}, and {@link
   * TreeMultimap#create(Comparator, Comparator)} won't suffice.
   *
   * <p>Note: the multimap assumes complete ownership over of {@code map} and the collections
   * returned by {@code factory}. Those objects should not be manually updated and they should not

    /*
     * TODO(lowasser): consider checking for ImmutableAsList here
     * TODO(lowasser): consider checking for Multiset here
     */
    // Don't refer to ImmutableSortedSet by name so it won't pull in all that code
    if (elements instanceof ImmutableSet && !(elements instanceof SortedSet)) {
      @SuppressWarnings("unchecked") // all supported methods are covariant

        Object element = entry.getElement();
        int entryCount = entry.getCount();
        if (entryCount != 0) {
          // Safe as long as we never add a new entry, which we won't.
          // (Presumably it can still throw CCE/NPE but only if the underlying Multiset does.)
          @SuppressWarnings({"unchecked", "nullness"})

    return new HashSet<>();
  }

  /**
   * Creates a <i>mutable</i> {@code HashSet} instance initially containing the given elements.
   *
   * <p><b>Note:</b> if elements are non-null and won't be added or removed after this point, use
   * {@link ImmutableSet#of()} or {@link ImmutableSet#copyOf(Object[])} instead. If {@code E} is an

      // meant that sometimes a too-large threshold is calculated. However, this new threshold is
      // independent of the initial capacity, except that it won't be lower than the threshold
      // computed from that capacity. Because the internal table is only allocated on the first
      // write, we won't see copying because of the new threshold. So it is always OK to use the
      // calculation here.
      return (int) Math.ceil(expectedSize / 0.75);

    * Only applications using forms (e.g. file uploads) could be affected.
    * For most cases, upgrading won't have any breaking changes.

## 0.91.0

### Upgrades

    *   Added a new constructor argument `experimental_enable_variable_lifting`
        to `tf.Variable`, defaulting to True. When it's `False`, the variable
        won't be lifted out of `tf.function`, thus it can be used as a
        `tf.function`-local variable: during each execution of the
        `tf.function`, the variable will be created and then disposed, similar