/** Test an empty collection. */
  ZERO(0),
  /** Test a one-element collection. */
  ONE(1),
  /** Test a three-element collection. */
  SEVERAL(3),
  /*
   * TODO: add VERY_LARGE, noting that we currently assume that the fourth
   * sample element is not in any collection
   */

  ANY(ZERO, ONE, SEVERAL);

  private final Set<Feature<? super Collection>> implied;

#                 ; [group-name] = map:{
#                     ; groupComment=[comment]
#                     ; elementList=list:{[the list of classification element's name]}
#                 }
#             }
#         }
#         # classification elements for implicit classification
#         ; map:{
#             ; code=[code]; name=[name]; alias=[alias]; comment=[comment]

    collection = getSubjectGenerator().create(arrayAndDuplicate.elements);
    E duplicate = arrayAndDuplicate.duplicate;

    int firstIndex = getList().indexOf(duplicate);
    int initialSize = getList().size();
    assertTrue("remove(present) should return true", getList().remove(duplicate));
    assertTrue(
        "After remove(duplicate), a list should still contain the duplicate element",
        getList().contains(duplicate));
    assertFalse(

    };
  }

  // TODO b/327389044 - `Set<? extends Object> elements` should be enough but J2KT needs the <E>
  private static <E> void assertPowerSetHashCode(int expected, Set<E> elements) {
    assertEquals(expected, powerSet(elements).hashCode());
  }

  private static void assertPowerSetSize(int i, Object... elements) {
    assertEquals(i, powerSet(newHashSet(elements)).size());
  }

   * IllegalArgumentException}.
   */
  boolean allowsSelfLoops();

  /** Returns the order of iteration for the elements of {@link #nodes()}. */
  ElementOrder<N> nodeOrder();

  /** Returns the order of iteration for the elements of {@link #edges()}. */
  ElementOrder<E> edgeOrder();

  //
  // Element-level accessors
  //

  /**

   *       href="https://github.com/google/guava/wiki/GraphsExplained#graph-elements-nodes-and-edges">
   *       graph elements</a> for details)
   * </ul>
   *
   * @throws IllegalArgumentException if {@code node} is not an element of this graph
   */
  Iterable<? extends N> successors(N node);

    }

    @Override
    public @Nullable E peek() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.peek();
    }

    @Override
    public E element() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.element();
    }

    @Override
    public Iterator<E> iterator() {
      // We explicitly don't lock for iterator()
      assertFalse(Thread.holdsLock(mutex));

    public static final String CONTAINS = "contains:";

    /** XML element name for collections container. */
    protected static final String COLLECTIONS = "collections";

    /** XML element name for individual collection. */
    protected static final String COLLECTION = "collection";

    /** XML element name for global parameters container. */
    protected static final String GLOBALPARAMS = "globalparams";

    final BlockingQueue<Object> q;
    final int elements;
    final CountDownLatch beganProducing = new CountDownLatch(1);
    final CountDownLatch doneProducing = new CountDownLatch(1);

    Producer(BlockingQueue<Object> q, int elements) {
      this.q = q;
      this.elements = elements;
    }

    @Override
    public @Nullable Void call() throws InterruptedException {

    }

    @Override
    public @Nullable E peek() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.peek();
    }

    @Override
    public E element() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.element();
    }

    @Override
    public Iterator<E> iterator() {
      // We explicitly don't lock for iterator()
      assertFalse(Thread.holdsLock(mutex));