@CollectionFeature.Require(SUPPORTS_REMOVE)
  public void testRetainAllIgnoresCount() {
    initThreeCopies();
    List<E> contents = Helpers.copyToList(getMultiset());
    assertFalse(getMultiset().retainAll(Collections.singleton(e0())));
    expectContents(contents);
  }

  /**
   * Returns {@link Method} instances for the remove tests that assume multisets support duplicates

   * the set is the same as the ordering of the given contents.
   */
  private static <E> void verifyLinkedHashSetContents(
      LinkedHashSet<E> set, Collection<E> contents) {
    assertEquals(
        "LinkedHashSet should have preserved order for iteration",
        new ArrayList<E>(set),
        new ArrayList<E>(contents));
    verifySetContents(set, contents);
  }

  /**

import java.util.function.Function;
import java.util.stream.Collector;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A {@link RangeMap} whose contents will never change, with many other important properties
 * detailed at {@link ImmutableCollection}.
 *
 * @author Louis Wasserman
 * @since 14.0
 */
@GwtIncompatible // NavigableMap
@ElementTypesAreNonnullByDefault

   * PermittedMetaException}.
   */
  protected final class MultiExceptionListIterator implements ListIterator<E> {
    // TODO: track seen elements when order isn't guaranteed
    // TODO: verify contents afterward
    // TODO: something shiny and new instead of Stack
    // TODO: test whether null is supported (create a Feature)
    /**

    throwIfUnchecked(throwable);
    throw new RuntimeException(throwable);
  }

  /**
   * Returns the innermost cause of {@code throwable}. The first throwable in a chain provides
   * context from when the error or exception was initially detected. Example usage:
   *
   * <pre>
   * assertEquals("Unable to assign a customer id", Throwables.getRootCause(e).getMessage());
   * </pre>
   *

    throwIfUnchecked(throwable);
    throw new RuntimeException(throwable);
  }

  /**
   * Returns the innermost cause of {@code throwable}. The first throwable in a chain provides
   * context from when the error or exception was initially detected. Example usage:
   *
   * <pre>
   * assertEquals("Unable to assign a customer id", Throwables.getRootCause(e).getMessage());
   * </pre>
   *

  }

  /**
   * Converts an iterable into a collection. If the iterable is already a collection, it is
   * returned. Otherwise, an {@link java.util.ArrayList} is created with the contents of the
   * iterable in the same iteration order.
   */
  private static <E extends @Nullable Object> Collection<E> castOrCopyToCollection(
      Iterable<E> iterable) {
    return (iterable instanceof Collection)

   * constructed multimap. The new multimap has the same {@link Multimap#entries()} iteration order
   * as the input multimap, except for excluding duplicate mappings.
   *
   * @param multimap the multimap whose contents are copied to this multimap
   */
  public static <K extends @Nullable Object, V extends @Nullable Object>
      LinkedHashMultimap<K, V> create(Multimap<? extends K, ? extends V> multimap) {

import java.util.stream.Collector;
import java.util.stream.Stream;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A {@link SetMultimap} whose contents will never change, with many other important properties
 * detailed at {@link ImmutableCollection}.
 *
 * <p><b>Warning:</b> As in all {@link SetMultimap}s, do not modify either a key <i>or a value</i>

import java.util.stream.Collector;
import java.util.stream.Collectors;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A {@link NavigableMap} whose contents will never change, with many other important properties
 * detailed at {@link ImmutableCollection}.
 *
 * <p><b>Warning:</b> as with any sorted collection, you are strongly advised not to use a {@link