} catch (RuntimeException tolerated) {
      // GWT's HashMap.keySet().removeAll(null) doesn't throws NPE.
    }
  }

  @Override
  public void testKeySetRetainAllNullFromEmpty() {
    try {
      super.testKeySetRetainAllNullFromEmpty();
    } catch (RuntimeException tolerated) {
      // GWT's HashMap.keySet().retainAll(null) doesn't throws NPE.
    }
  }

  @Override

  }

  @MapFeature.Require(SUPPORTS_PUT)
  @CollectionSize.Require(absent = ZERO)
  public void testPutPresentKeyPropagatesToGet() {
    List<K> keys = copyToList(multimap().keySet());
    for (K key : keys) {
      resetContainer();

      int size = getNumElements();

      Collection<V> collection = multimap().get(key);
      Collection<V> expectedCollection = copyToList(collection);

  }

  @MapFeature.Require(SUPPORTS_PUT)
  @CollectionSize.Require(absent = ZERO)
  public void testPutPresentKeyPropagatesToGet() {
    List<K> keys = copyToList(multimap().keySet());
    for (K key : keys) {
      resetContainer();

      int size = getNumElements();

      Collection<V> collection = multimap().get(key);
      Collection<V> expectedCollection = copyToList(collection);

  }

  @CollectionSize.Require(absent = ZERO)
  @MapFeature.Require({SUPPORTS_PUT, SUPPORTS_REMOVE})
  public void testReplaceNonEmptyValues() {
    List<K> keys = copyToList(multimap().keySet());
    List<V> values = asList(v0(), v2(), v3());

    for (K k : keys) {
      resetContainer();

      int size = multimap().size();
      Collection<V> oldKeyValues = copyToList(multimap().get(k));

    return Collections.unmodifiableSet(adjacentNodeValues.keySet());
  }

  @Override
  public Set<N> predecessors() {
    return adjacentNodes();
  }

  @Override
  public Set<N> successors() {
    return adjacentNodes();
  }

  @Override
  public Iterator<EndpointPair<N>> incidentEdgeIterator(N thisNode) {
    return Iterators.transform(
        adjacentNodeValues.keySet().iterator(),

   *
   * <p>The collections returned by {@link Multimap#keySet()}, {@link Multimap#keys()}, and {@link
   * Multimap#asMap()} will iterate through the keys in sorted order.
   *
   * <p>For all multimaps generated by the resulting builder, the {@link Multimap#keySet()} can be
   * safely cast to a {@link java.util.SortedSet}, and the {@link Multimap#asMap()} can safely be

   *
   * <p>The collections returned by {@link Multimap#keySet()}, {@link Multimap#keys()}, and {@link
   * Multimap#asMap()} will iterate through the keys in sorted order.
   *
   * <p>For all multimaps generated by the resulting builder, the {@link Multimap#keySet()} can be
   * safely cast to a {@link java.util.SortedSet}, and the {@link Multimap#asMap()} can safely be

    this(new TreeMap<K, V>(map));
  }

  private SafeTreeMap(NavigableMap<K, V> delegate) {
    this.delegate = delegate;
    if (delegate == null) {
      throw new NullPointerException();
    }
    for (K k : keySet()) {
      checkValid(k);
    }
  }

  @Override
  public @Nullable Entry<K, V> ceilingEntry(K key) {
    return delegate.ceilingEntry(checkValid(key));
  }

  @Override

    this(new TreeMap<K, V>(map));
  }

  private SafeTreeMap(NavigableMap<K, V> delegate) {
    this.delegate = delegate;
    if (delegate == null) {
      throw new NullPointerException();
    }
    for (K k : keySet()) {
      checkValid(k);
    }
  }

  @Override
  public @Nullable Entry<K, V> ceilingEntry(K key) {
    return delegate.ceilingEntry(checkValid(key));
  }

  @Override

    } catch (RuntimeException tolerated) {
      // GWT's TreeMap.keySet().removeAll(null) doesn't throws NPE.
    }
  }

  @Override
  public void testKeySetRetainAllNullFromEmpty() {
    try {
      super.testKeySetRetainAllNullFromEmpty();
    } catch (RuntimeException tolerated) {
      // GWT's TreeMap.keySet().retainAll(null) doesn't throws NPE.
    }
  }

  @Override