assume().that(graphIsMutable()).isTrue();

    addEdge(N1, N2, E12);
    @SuppressWarnings("unused")
    EndpointPair<Integer> unused =
        networkAsMutableNetwork.incidentNodes(E12); // ensure cache (if any) is populated
    assertTrue(networkAsMutableNetwork.removeEdge(E12));
    assertEdgeNotInGraphErrorMessage(
        assertThrows(

      NavigableMap<K, V> synchronizedNavigableMap(NavigableMap<K, V> navigableMap) {
    return Synchronized.navigableMap(navigableMap);
  }

  /**
   * {@code AbstractMap} extension that makes it easy to cache customized keySet, values, and
   * entrySet views.
   */
  @GwtCompatible
  abstract static class ViewCachingAbstractMap<
          K extends @Nullable Object, V extends @Nullable Object>

         * It's very unlikely that any loaded Futures class will see getChecked called with more
         * than a handful of exceptions. But it seems prudent to set a cap on how many we'll cache.
         * This avoids out-of-control memory consumption, and it keeps the cache from growing so
         * large that doing the lookup is noticeably slower than redoing the work would be.
         *

      return new SampleElements<>("one", "two", "three", "four", "five");
    }

    @Override
    public SampleElements<String> sampleValues() {
      return new SampleElements<>("january", "february", "march", "april", "may");
    }

    @Override
    public Collection<String> createCollection(Iterable<? extends String> values) {
      return Lists.newArrayList(values);
    }

    @Override

   */
  public static final String SEC_CH_UA = "Sec-CH-UA";
  /**
   * The HTTP <a href="https://wicg.github.io/ua-client-hints/#sec-ch-ua-arch">{@code
   * Sec-CH-UA-Arch}</a> header field name.
   *
   * @since 30.0
   */
  public static final String SEC_CH_UA_ARCH = "Sec-CH-UA-Arch";
  /**
   * The HTTP <a href="https://wicg.github.io/ua-client-hints/#sec-ch-ua-model">{@code
   * Sec-CH-UA-Model}</a> header field name.

 * @author Jon Noack
 */
@GwtIncompatible // not worth using in GWT for now
@ElementTypesAreNonnullByDefault
class CompactHashSet<E extends @Nullable Object> extends AbstractSet<E> implements Serializable {
  // TODO(user): cache all field accesses in local vars

  /** Creates an empty {@code CompactHashSet} instance. */
  public static <E extends @Nullable Object> CompactHashSet<E> create() {
    return new CompactHashSet<>();
  }

  /**