/**
   * Returns true if this graph allows self-loops (edges that connect a node to itself). Attempting
   * to add a self-loop to a graph that does not allow them will throw an {@link
   * IllegalArgumentException}.
   */
  @Override
  boolean allowsSelfLoops();

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

  /**

    assertThrows(IllegalArgumentException.class, () -> registry.unregister(new StringSubscriber()));

    StringSubscriber s1 = new StringSubscriber();
    registry.register(s1);
    assertThrows(IllegalArgumentException.class, () -> registry.unregister(new StringSubscriber()));

    registry.unregister(s1);

    assertThrows(IllegalArgumentException.class, () -> registry.unregister(s1));
  }

              e -> e instanceof ConcurrentModificationException)
          .put(ExecutionException.class, e -> e instanceof ExecutionException)
          .put(IllegalArgumentException.class, e -> e instanceof IllegalArgumentException)
          .put(IllegalStateException.class, e -> e instanceof IllegalStateException)
          .put(IndexOutOfBoundsException.class, e -> e instanceof IndexOutOfBoundsException)

              e -> e instanceof ConcurrentModificationException)
          .put(ExecutionException.class, e -> e instanceof ExecutionException)
          .put(IllegalArgumentException.class, e -> e instanceof IllegalArgumentException)
          .put(IllegalStateException.class, e -> e instanceof IllegalStateException)
          .put(IndexOutOfBoundsException.class, e -> e instanceof IndexOutOfBoundsException)

              e -> e instanceof ConcurrentModificationException)
          .put(ExecutionException.class, e -> e instanceof ExecutionException)
          .put(IllegalArgumentException.class, e -> e instanceof IllegalArgumentException)
          .put(IllegalStateException.class, e -> e instanceof IllegalStateException)
          .put(IndexOutOfBoundsException.class, e -> e instanceof IndexOutOfBoundsException)

      // the range have a lower bound
      throw new IllegalArgumentException(
          "Neither the DiscreteDomain nor this range set are bounded below");
    } else if (!span.hasUpperBound()) {
      try {
        domain.maxValue();
      } catch (NoSuchElementException e) {
        throw new IllegalArgumentException(
            "Neither the DiscreteDomain nor this range set are bounded above");
      }

    try {
      multiset.add(entry.getElement(), entry.getCount());
      fail("Expected IllegalArgumentException");
    } catch (IllegalArgumentException expected) {
    }

    try {
      multiset.add(entry.getElement());
      fail("Expected IllegalArgumentException");
    } catch (IllegalArgumentException expected) {
    }

    try {
      multiset.addAll(singletonList(entry.getElement()));

@GwtCompatible
@ElementTypesAreNonnullByDefault
public interface BiMap<K extends @Nullable Object, V extends @Nullable Object> extends Map<K, V> {
  // Modification Operations

  /**
   * {@inheritDoc}
   *
   * @throws IllegalArgumentException if the given value is already bound to a different key in this
   *     bimap. The bimap will remain unmodified in this event. To avoid this exception, call {@link
   *     #forcePut} instead.
   */

   *
   * @throws IllegalArgumentException if duplicate keys are provided
   */
  public static <K, V> ImmutableMap<K, V> of(K k1, V v1, K k2, V v2) {
    return RegularImmutableMap.fromEntries(entryOf(k1, v1), entryOf(k2, v2));
  }

  /**
   * Returns an immutable map containing the given entries, in order.
   *
   * @throws IllegalArgumentException if duplicate keys are provided
   */

 * hostname. Building APIs that consume such malformed values is difficult!
 *
 * This class has a modern API. It avoids punitive checked exceptions: [toHttpUrl] throws
 * [IllegalArgumentException] on invalid input or [toHttpUrlOrNull] returns null if the input is an
 * invalid URL. You can even be explicit about whether each component has been encoded already.
 *