};

    abstract <T> Iterable<T> view(T root, TreeTraverser<T> viewer);
  }

  private Iterable<BinaryNode> view;

  @Param Topology topology;

  @Param({"1", "100", "10000", "1000000"})
  int size;

  @Param Traversal traversal;

  @Param({"1234"})
  SpecialRandom rng;

  @BeforeExperiment
  void setUp() {
    this.view = traversal.view(topology.createTree(size, rng).get(), VIEWER);

  /**
   * Returns a descending view of this multiset. Modifications made to either map will be reflected
   * in the other.
   */
  SortedMultiset<E> descendingMultiset();

  /**
   * Returns a view of this multiset restricted to the elements less than {@code upperBound},
   * optionally including {@code upperBound} itself. The returned multiset is a view of this

 * ...
 * }</pre>
 *
 * <h3>Views</h3>
 *
 * <p>Much of the power of the multimap API comes from the <i>view collections</i> it provides.
 * These always reflect the latest state of the multimap itself. When they support modification, the
 * changes are <i>write-through</i> (they automatically update the backing multimap). These view
 * collections are:
 *
 * <ul>
 *   <li>{@link #asMap}, mentioned above

    assertEquals(expected, view);
    assertEquals(expected.asRanges(), view.asRanges());
    assertEquals(expected.isEmpty(), view.isEmpty());

    if (!expected.isEmpty()) {
      assertEquals(expected.span(), view.span());
    }

    for (int i = MIN_BOUND - 1; i <= MAX_BOUND + 1; i++) {
      assertEquals(expected.contains(i), view.contains(i));

   *
   * @param multiset the multiset for which an unmodifiable view is to be generated
   * @return an unmodifiable view of the multiset
   */
  public static <E extends @Nullable Object> Multiset<E> unmodifiableMultiset(
      Multiset<? extends E> multiset) {
    if (multiset instanceof UnmodifiableMultiset || multiset instanceof ImmutableMultiset) {

 *   <li>Offers useful operations beyond just {@code get} and {@code length}, so you don't have to
 *       hunt through classes like {@link Arrays} and {@link Ints} for them.
 *   <li>Supports a copy-free {@link #subArray} view, so methods that accept this type don't need to
 *       add overloads that accept start and end indexes.
 *   <li>Access to all collection-based utilities via {@link #asList} (though at the cost of
 *       allocating garbage).

            iterator.remove();
          }
        };
      }
    };
  }

  /**
   * Returns a view of {@code iterable} containing its first {@code limitSize} elements. If {@code
   * iterable} contains fewer than {@code limitSize} elements, the returned view contains all of its
   * elements. The returned iterable's iterator supports {@code remove()} if {@code iterable}'s
   * iterator does.
   *

    } else {
      return new WrappedSortedSet(key, (SortedSet<V>) collection, null);
    }
  }

  // Following Javadoc copied from Multimap and SortedSetMultimap.

  /**
   * Returns a collection view of all values associated with a key. If no mappings in the multimap
   * have the provided key, an empty collection is returned.
   *
   * <p>Changes to the returned collection will update the underlying multimap, and vice versa.

    } else {
      return new WrappedSortedSet(key, (SortedSet<V>) collection, null);
    }
  }

  // Following Javadoc copied from Multimap and SortedSetMultimap.

  /**
   * Returns a collection view of all values associated with a key. If no mappings in the multimap
   * have the provided key, an empty collection is returned.
   *
   * <p>Changes to the returned collection will update the underlying multimap, and vice versa.

 *   <li>Offers useful operations beyond just {@code get} and {@code length}, so you don't have to
 *       hunt through classes like {@link Arrays} and {@link Doubles} for them.
 *   <li>Supports a copy-free {@link #subArray} view, so methods that accept this type don't need to
 *       add overloads that accept start and end indexes.
 *   <li>Access to all collection-based utilities via {@link #asList} (though at the cost of
 *       allocating garbage).