// notification.
    assertThat(Sets.union(cache.asMap().keySet(), removalNotifications.keySet()))
        .isEqualTo(expectedKeys);
    assertThat(cache.asMap().keySet()).containsNoneIn(removalNotifications.keySet());
    threadPool.shutdown();
    threadPool.awaitTermination(300, SECONDS);
  }

  /**

    // TODO(lowasser): make this trigger only if the map is a submap
    // currently, the KeySetGenerator won't work properly for a subset of a keyset of a submap
    keySetFeatures.add(CollectionFeature.SUBSET_VIEW);
    if (mapFeatures.contains(MapFeature.ALLOWS_NULL_KEYS)) {
      keySetFeatures.add(CollectionFeature.ALLOWS_NULL_VALUES);

      ImmutableMap.Builder<String, Integer> builder = ImmutableMap.builder();
      for (int i = 0; i < elements.length; i++) {
        builder.put(elements[i], i);
      }
      return builder.buildOrThrow().keySet().asList();
    }
  }

  public static class ImmutableMapValueListGenerator extends TestStringListGenerator {
    @Override
    public List<String> create(String[] elements) {

  }

  @Override
  Map<K, Collection<V>> createAsMap() {
    return new AsMap();
  }

  @Override
  Set<K> createKeySet() {
    return asMap().keySet();
  }

  boolean removeEntriesIf(Predicate<? super Entry<K, Collection<V>>> predicate) {
    Iterator<Entry<K, Collection<V>>> entryIterator = unfiltered.asMap().entrySet().iterator();
    boolean changed = false;

    return MoreObjects.firstNonNull(
        (ImmutableMap<R, V>) columnMap().get(columnKey), ImmutableMap.of());
  }

  @Override
  public ImmutableSet<C> columnKeySet() {
    return columnMap().keySet();
  }

  /**
   * {@inheritDoc}
   *
   * <p>The value {@code Map<R, V>} instances in the returned map are {@link ImmutableMap} instances
   * as well.
   */
  @Override

  // views

  /**
   * Returns an immutable set of the distinct keys in this multimap, in the same order as they
   * appear in this multimap.
   */
  @Override
  public ImmutableSet<K> keySet() {
    return map.keySet();
  }

  @Override
  Set<K> createKeySet() {
    throw new AssertionError("unreachable");
  }

  /**

    }

    assertEquals(values.size(), multimap().get(key).size());

    assertEquals(values.size() > 0, multimap().containsKey(key));
    assertEquals(values.size() > 0, multimap().keySet().contains(key));
    assertEquals(values.size() > 0, multimap().keys().contains(key));
  }

  protected final K k0() {
    return e0().getKey();
  }

  protected final V v0() {

                    }
                    return multimap.keySet();
                  }

                  @Override
                  public List<String> order(List<String> insertionOrder) {
                    return Ordering.natural().nullsFirst().sortedCopy(insertionOrder);
                  }
                })
            .named("TreeMultimap.keySet")
            .withFeatures(

        };

    ServiceManager manager = new ServiceManager(asList(a));
    manager.startAsync();
    manager.stopAsync();
    manager.awaitStopped(10, MILLISECONDS);
    assertThat(manager.servicesByState().keySet()).containsExactly(Service.State.TERMINATED);
  }

  public void testNotifyStoppedAfterFailure() throws TimeoutException {
    Service a =
        new AbstractService() {
          @Override

  @CollectionSize.Require(absent = ZERO)
  public void testPutAbsentConcurrentWithKeySetIteration() {
    assertThrows(
        ConcurrentModificationException.class,
        () -> {
          Iterator<K> iterator = getMap().keySet().iterator();
          put(e3());
          iterator.next();
        });
  }

  @MapFeature.Require({FAILS_FAST_ON_CONCURRENT_MODIFICATION, SUPPORTS_PUT})
  @CollectionSize.Require(absent = ZERO)