*
   * @param anElement one of the elements the set should contain
   * @param otherElements the rest of the elements the set should contain
   * @return an immutable set containing those elements, minus duplicates
   */
  public static <E extends Enum<E>> ImmutableSet<E> immutableEnumSet(
      E anElement, E... otherElements) {
    return ImmutableEnumSet.asImmutable(EnumSet.of(anElement, otherElements));
  }

  /**

        map.put(FieldNames.TIMESTAMP, timestamp.toInstant().toEpochMilli());
        return map;
    }

    /**
     * Concatenates values to a destination list, avoiding duplicates.
     * @param dest The destination list.
     * @param newValues The new values to add.
     * @param <T> The type of the values.
     */

    }
  }

  // TODO: test adding element of wrong type

  /**
   * Returns {@link Method} instances for the {@code setCount()} tests that assume multisets support
   * duplicates so that the test of {@code Multisets.forSet()} can suppress them.
   */
  @J2ktIncompatible
  @GwtIncompatible // reflection
  public static List<Method> getSetCountDuplicateInitializingMethods() {
    return asList(

   * collection in unspecified order.
   *
   * @param collection the elements that the set should contain
   * @return a new {@code CompactHashSet} containing those elements (minus duplicates)
   */
  public static <E extends @Nullable Object> CompactHashSet<E> create(
      Collection<? extends E> collection) {
    CompactHashSet<E> set = createWithExpectedSize(collection.size());
    set.addAll(collection);

    return Ordering.from(comparator).immutableSortedCopy((Iterable<@NonNull E>) getDelegate());
  }

  /**
   * Returns an {@code ImmutableSet} containing all of the elements from this fluent iterable with
   * duplicates removed.
   *
   * <p><b>{@code Stream} equivalent:</b> pass {@link ImmutableSet#toImmutableSet} to {@code
   * stream.collect()}.
   *
   * @throws NullPointerException if any element is {@code null}

   */

  /*
   * These generators also rely on consecutive integer inputs (not necessarily in order, but no
   * holes).
   */

  // SetCreationTester has some tests that pass in duplicates. Dedup them.
  private static <E extends Comparable<? super E>> SortedSet<E> nullCheckedTreeSet(E[] elements) {
    SortedSet<E> set = newTreeSet();
    for (E element : elements) {

   * @param columnKeys column keys that may be stored in the generated table
   * @throws NullPointerException if any of the provided keys is null
   * @throws IllegalArgumentException if {@code rowKeys} or {@code columnKeys} contains duplicates
   *     or if exactly one of {@code rowKeys} or {@code columnKeys} is empty.
   */
  public static <R, C, V> ArrayTable<R, C, V> create(
      Iterable<? extends R> rowKeys, Iterable<? extends C> columnKeys) {

   * update the underlying table, and vice versa.
   *
   * @return set of column keys
   */
  Set<C> columnKeySet();

  /**
   * Returns a collection of all values, which may contain duplicates. Changes to the returned
   * collection will update the underlying table, and vice versa.
   *
   * @return collection of values
   */
  Collection<V> values();

  /**

   with its <<<DefaultModelValidator>>> implementation
   ({{{./xref/org/apache/maven/model/validation/DefaultModelValidator.html}source}})

   ** model normalization - merge duplicates: <<<ModelNormalizer>>> ({{{./apidocs/org/apache/maven/model/normalization/ModelNormalizer.html}javadoc}}),
   with its <<<DefaultModelNormalizer>>> implementation

        SuggestItem.Kind[] result = SuggestItem.concatKinds(kinds1, kinds2);

        assertNotNull(result);
        assertEquals(2, result.length); // Should not have duplicates
        assertTrue(Arrays.asList(result).contains(SuggestItem.Kind.QUERY));
        assertTrue(Arrays.asList(result).contains(SuggestItem.Kind.DOCUMENT));
    }

    @Test
    public void testEmptySource() {