static boolean removeAllImpl(Multiset<?> self, Collection<?> elementsToRemove) {
    Collection<?> collection =
        (elementsToRemove instanceof Multiset)
            ? ((Multiset<?>) elementsToRemove).elementSet()
            : elementsToRemove;

    return self.elementSet().removeAll(collection);
  }

  /** An implementation of {@link Multiset#retainAll}. */

   * half of that is more awkward to arrange...
   */
  private static <T> Iterable<T> iterable(Collection<T> collection) {
    // return collection::iterator;
    return new Iterable<T>() {
      @Override
      public Iterator<T> iterator() {
        return collection.iterator();
      }
    };
  }

  public void testEquals() {
    new EqualsTester()

        return false;
      }

      @Override
      public boolean removeAll(Collection<?> collection) {
        return removeAllKeys(unfiltered, predicate, collection);
      }

      @Override
      public boolean retainAll(Collection<?> collection) {
        return retainAllKeys(unfiltered, predicate, collection);
      }

      @Override
      public @Nullable Object[] toArray() {

        return false;
      }

      @Override
      public boolean removeAll(Collection<?> collection) {
        return removeAllKeys(unfiltered, predicate, collection);
      }

      @Override
      public boolean retainAll(Collection<?> collection) {
        return retainAllKeys(unfiltered, predicate, collection);
      }

      @Override
      public @Nullable Object[] toArray() {

  public void testAsSetIteration() {
    Set<Entry<String, Collection<Integer>>> set =
        new LinkedHashSet<>(
            asList(
                immutableEntry("foo", (Collection<Integer>) newHashSet(2, 3, 6)),
                immutableEntry("bar", (Collection<Integer>) newHashSet(4, 5, 10, 11)),
                immutableEntry("baz", (Collection<Integer>) newHashSet(7, 8)),

    assertTrue(copy instanceof ImmutableMultiset);
    return copy;
  }

  @CanIgnoreReturnValue
  @GwtIncompatible // SerializableTester
  static <E> Collection<E> reserializeAndAssertElementsEqual(Collection<E> original) {
    Collection<E> copy = reserialize(original);
    assertTrue(elementsEqual(original, copy));
    assertTrue(copy instanceof ImmutableCollection);
    return copy;
  }

     *
     * @see org.apache.maven.api.services.ArtifactResolver#resolve(Session, Collection)
     */
    @Nonnull
    Collection<DownloadedArtifact> resolveArtifacts(@Nonnull Collection<? extends ArtifactCoordinates> coordinates);

    /**
     * Shortcut for {@code getService(ArtifactResolver.class).resolve(...)}.
     *

        Object value = ee.evaluate("${mojo.plugin.dependencies}");

        assertInstanceOf(Collection.class, value);

        @SuppressWarnings("unchecked")
        Collection<Artifact> artifacts = (Collection<Artifact>) value;

        assertEquals(1, artifacts.size());

        Artifact result = artifacts.iterator().next();

        return mainArtifact.flatMap(artifactManager::getPath);
    }

    @Nonnull
    @Override
    public Collection<ProducedArtifact> getAttachedArtifacts(@Nonnull Project project) {
        requireNonNull(project, "project" + " cannot be null");
        Collection<ProducedArtifact> attached =
                map(getMavenProject(project).getAttachedArtifacts(), a -> getSession(project)

 * </p>
 *
 * <pre>
 * import static org.codelibs.core.collection.IndexedIterator.*;
 *
 * List&lt;String&gt; list = ...;
 * for (Indexed&lt;String&gt; indexed : indexed(list)) {
 *     System.out.println(indexed.getIndex());
 *     System.out.println(indexed.getElement());
 * }
 * </pre>
 *
 * <pre>
 * import static org.codelibs.core.collection.IndexedIterator.*;
 * import static org.codelibs.core.io.LineIterator.*;