* href="ImmutableMultimap.html#iteration">grouped by key</a>.
   *
   * <p>Example:
   *
   * <pre>{@code
   * static final Multimap<Character, String> FIRST_LETTER_MULTIMAP =
   *     Stream.of("banana", "apple", "carrot", "asparagus", "cherry")
   *         .collect(toImmutableListMultimap(str -> str.charAt(0), str -> str.substring(1)));
   *
   * // is equivalent to
   *
   * static final Multimap<Character, String> FIRST_LETTER_MULTIMAP =

   * e ---- c ---- f
   * }</pre>
   */
  private static final SuccessorsFunction<Character> JAVADOC_GRAPH =
      createUndirectedGraph("ba", "ad", "be", "ac", "ec", "cf");

  /**
   * A diamond shaped directed graph (arrows going down):
   *
   * <pre>{@code
   *   a
   *  / \
   * b   c
   *  \ /
   *   d
   * }</pre>
   */
  private static final SuccessorsFunction<Character> DIAMOND_GRAPH =

   * the given class. If the object being tested is {@code null} this predicate evaluates to {@code
   * false}.
   *
   * <p>If you want to filter an {@code Iterable} to narrow its type, consider using {@link
   * com.google.common.collect.Iterables#filter(Iterable, Class)} in preference.
   *
   * <p><b>Warning:</b> contrary to the typical assumptions about predicates (as documented at

    filled.putAll('c', Arrays.asList('h', 'e', 'r', 'r', 'y'));
    CollectorTester.of(collector, equivalence)
        .expectCollects(empty)
        .expectCollects(filled, "banana", "apple", "carrot", "asparagus", "cherry");
  }

  @SuppressWarnings("deprecation")
  public void testUnmodifiableListMultimapShortCircuit() {
    ListMultimap<String, Integer> mod = ArrayListMultimap.create();

   *
   * <p>Example:
   *
   * <pre>{@code
   * static final ListMultimap<Character, String> FIRST_LETTER_MULTIMAP =
   *     Stream.of("banana", "apple", "carrot", "asparagus", "cherry")
   *         .collect(
   *             toMultimap(
   *                  str -> str.charAt(0),
   *                  str -> str.substring(1),