public static <T extends @Nullable Object> UnmodifiableIterator<T> unmodifiableIterator(
      Iterator<? extends T> iterator) {
    checkNotNull(iterator);
    if (iterator instanceof UnmodifiableIterator) {
      @SuppressWarnings("unchecked") // Since it's unmodifiable, the covariant cast is safe
      UnmodifiableIterator<T> result = (UnmodifiableIterator<T>) iterator;
      return result;
    }

  final transient Collection<E> delegate;

  ForwardingImmutableCollection(Collection<E> delegate) {
    this.delegate = delegate;
  }

  @Override
  public UnmodifiableIterator<E> iterator() {
    return Iterators.unmodifiableIterator(delegate.iterator());
  }

  @Override
  public boolean contains(@Nullable Object object) {
    return object != null && delegate.contains(object);
  }

  @Override

    return delegateList().equals(obj);
  }

  @Override
  public int hashCode() {
    return delegateList().hashCode();
  }

  @Override
  public UnmodifiableIterator<E> iterator() {
    return Iterators.unmodifiableIterator(delegateList().iterator());
  }

  @Override
  public boolean contains(@Nullable Object object) {
    return object != null && delegateList().contains(object);
  }

  }

  // This declaration is needed to make Set.iterator() and
  // ImmutableCollection.iterator() appear consistent to javac's type inference.
  @Override
  public abstract UnmodifiableIterator<E> iterator();

  abstract static class CachingAsList<E> extends ImmutableSet<E> {
    @LazyInit private transient ImmutableList<E> asList;

    @Override
    public ImmutableList<E> asList() {

  }

  ImmutableSet<K> createKeySet() {
    return new ImmutableMapKeySet<K, V>(this);
  }

  UnmodifiableIterator<K> keyIterator() {
    final UnmodifiableIterator<Entry<K, V>> entryIterator = entrySet().iterator();
    return new UnmodifiableIterator<K>() {
      @Override
      public boolean hasNext() {
        return entryIterator.hasNext();
      }

      @Override

    this.map = map;
  }

  @Override
  public int size() {
    return map.size();
  }

  @Override
  public UnmodifiableIterator<V> iterator() {
    return new UnmodifiableIterator<V>() {
      final UnmodifiableIterator<Entry<K, V>> entryItr = map.entrySet().iterator();

      @Override
      public boolean hasNext() {
        return entryItr.hasNext();
      }

      @Override

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Iterators;
import com.google.common.collect.UnmodifiableIterator;
import java.util.AbstractSet;
import java.util.Map;
import org.jspecify.annotations.Nullable;

/**
 * A class to represent the set of edges connecting an (implicit) origin node to a target node.
 *

   * overrides it.
   */
  abstract ImmutableSet<K> createKeySet();

  UnmodifiableIterator<K> keyIterator() {
    UnmodifiableIterator<Entry<K, V>> entryIterator = entrySet().iterator();
    return new UnmodifiableIterator<K>() {
      @Override
      public boolean hasNext() {
        return entryIterator.hasNext();
      }

      @Override

  private ImmutableEnumSet(EnumSet<E> delegate) {
    this.delegate = delegate;
  }

  @Override
  boolean isPartialView() {
    return false;
  }

  @Override
  public UnmodifiableIterator<E> iterator() {
    return Iterators.unmodifiableIterator(delegate.iterator());
  }

  @Override
  public Spliterator<E> spliterator() {
    return delegate.spliterator();
  }

  @Override

  static final int SPLITERATOR_CHARACTERISTICS =
      Spliterator.IMMUTABLE | Spliterator.NONNULL | Spliterator.ORDERED;

  ImmutableCollection() {}

  @Override
  public abstract UnmodifiableIterator<E> iterator();

  @Override
  public boolean contains(@Nullable Object object) {
    return object != null && super.contains(object);
  }

  @Override
  public final boolean add(E e) {