* same structural relationships as those in this network.
   *
   * <p>Thus, two networks A and B are equal if <b>all</b> of the following are true:
   *
   * <ul>
   *   <li>A and B have equal {@link #isDirected() directedness}.
   *   <li>A and B have equal {@link #nodes() node sets}.
   *   <li>A and B have equal {@link #edges() edge sets}.
   *   <li>Every edge in A and B connects the same nodes in the same direction (if any).

   * same structural relationships as those in this graph.
   *
   * <p>Thus, two graphs A and B are equal if <b>all</b> of the following are true:
   *
   * <ul>
   *   <li>A and B have equal {@link #isDirected() directedness}.
   *   <li>A and B have equal {@link #nodes() node sets}.
   *   <li>A and B have equal {@link #edges() edge sets}.
   * </ul>
   *

   * same structural relationships as those in this graph.
   *
   * <p>Thus, two graphs A and B are equal if <b>all</b> of the following are true:
   *
   * <ul>
   *   <li>A and B have equal {@link #isDirected() directedness}.
   *   <li>A and B have equal {@link #nodes() node sets}.
   *   <li>A and B have equal {@link #edges() edge sets}.
   * </ul>
   *

   * the same structural relationships as those in this graph.
   *
   * <p>Thus, two value graphs A and B are equal if <b>all</b> of the following are true:
   *
   * <ul>
   *   <li>A and B have equal {@link #isDirected() directedness}.
   *   <li>A and B have equal {@link #nodes() node sets}.
   *   <li>A and B have equal {@link #edges() edge sets}.
   *   <li>The {@link #edgeValue(N, N) value} of a given edge is the same in both A and B.

   *       ContiguousSet.create(a, domain))}
   *   <li>uniqueness: unless {@code a.isEmpty()}, {@code ContiguousSet.create(a,
   *       domain).equals(ContiguousSet.create(b, domain))} implies {@code
   *       a.canonical(domain).equals(b.canonical(domain))}
   *   <li>idempotence: {@code a.canonical(domain).canonical(domain).equals(a.canonical(domain))}
   * </ul>
   *

  }

  /**
   * Implementation of the {@code equals}, {@code hashCode}, and {@code toString} methods of {@link
   * Multiset.Entry}.
   */
  abstract static class AbstractEntry<E extends @Nullable Object> implements Multiset.Entry<E> {
    /**
     * Indicates whether an object equals this entry, following the behavior specified in {@link
     * Multiset.Entry#equals}.
     */
    @Override

  }

  /**
   * Implementation of the {@code equals}, {@code hashCode}, and {@code toString} methods of {@link
   * Multiset.Entry}.
   */
  abstract static class AbstractEntry<E extends @Nullable Object> implements Multiset.Entry<E> {
    /**
     * Indicates whether an object equals this entry, following the behavior specified in {@link
     * Multiset.Entry#equals}.
     */
    @Override

    /**
     * Compares the specified object with this cell for equality. Two cells are equal when they have
     * equal row keys, column keys, and values.
     */
    @Override
    boolean equals(@CheckForNull Object obj);

    /**
     * Returns the hash code of this cell.
     *
     * <p>The hash code of a table cell is equal to {@link Objects#hashCode}{@code (e.getRowKey(),
     * e.getColumnKey(), e.getValue())}.

              K key = entry.getKey();
              Collection<V> collection =
                  filterCollection(entry.getValue(), new ValuePredicate(key));
              if (!collection.isEmpty() && c.equals(collection)) {
                if (collection.size() == entry.getValue().size()) {
                  entryIterator.remove();
                } else {
                  collection.clear();
                }

   * Chooses and returns the representative instance for any of a collection of instances that are
   * equal to each other. If two {@linkplain Object#equals equal} inputs are given to this method,
   * both calls will return the same instance. That is, {@code intern(a).equals(a)} always holds,
   * and {@code intern(a) == intern(b)} if and only if {@code a.equals(b)}. Note that {@code