*
 * @author Louis Wasserman
 */
@GwtIncompatible
public final class SafeTreeSet<E> implements Serializable, NavigableSet<E> {
  @SuppressWarnings("unchecked")
  private static final Comparator<Object> NATURAL_ORDER =
      (o1, o2) -> ((Comparable<Object>) o1).compareTo(o2);

  private final NavigableSet<E> delegate;

  public SafeTreeSet() {
    this(new TreeSet<E>());
  }

 *
 * @author Louis Wasserman
 */
@GwtIncompatible
public final class SafeTreeSet<E> implements Serializable, NavigableSet<E> {
  @SuppressWarnings("unchecked")
  private static final Comparator<Object> NATURAL_ORDER =
      (o1, o2) -> ((Comparable<Object>) o1).compareTo(o2);

  private final NavigableSet<E> delegate;

  public SafeTreeSet() {
    this(new TreeSet<E>());
  }

    }
  }

  @GwtIncompatible // NavigableSet
  private static final class FilteredNavigableSet<E extends @Nullable Object>
      extends FilteredSortedSet<E> implements NavigableSet<E> {
    FilteredNavigableSet(NavigableSet<E> unfiltered, Predicate<? super E> predicate) {
      super(unfiltered, predicate);
    }

    NavigableSet<E> unfiltered() {
      return (NavigableSet<E>) unfiltered;
    }

  }

  @Override
  @GwtIncompatible // NavigableSet
  public ImmutableSortedSet<E> descendingSet() {
    return forward;
  }

  @Override
  @GwtIncompatible // NavigableSet
  public UnmodifiableIterator<E> descendingIterator() {
    return forward.iterator();
  }

  @Override
  @GwtIncompatible // NavigableSet
  ImmutableSortedSet<E> createDescendingSet() {

    }
  }

  @GwtIncompatible // NavigableSet
  private static final class FilteredNavigableSet<E extends @Nullable Object>
      extends FilteredSortedSet<E> implements NavigableSet<E> {
    FilteredNavigableSet(NavigableSet<E> unfiltered, Predicate<? super E> predicate) {
      super(unfiltered, predicate);
    }

    NavigableSet<E> unfiltered() {
      return (NavigableSet<E>) unfiltered;
    }

  @WeakOuter
  final class WrappedNavigableSet extends WrappedSortedSet implements NavigableSet<V> {
    WrappedNavigableSet(
        @ParametricNullness K key, NavigableSet<V> delegate, @Nullable WrappedCollection ancestor) {
      super(key, delegate, ancestor);
    }

    @Override
    NavigableSet<V> getSortedSetDelegate() {
      return (NavigableSet<V>) super.getSortedSetDelegate();
    }

    @Override

  }

  @Override
  @GwtIncompatible // NavigableSet
  public ImmutableSortedSet<E> descendingSet() {
    return forward;
  }

  @Override
  @GwtIncompatible // NavigableSet
  public UnmodifiableIterator<E> descendingIterator() {
    return forward.iterator();
  }

  @Override
  @GwtIncompatible // NavigableSet
  ImmutableSortedSet<E> createDescendingSet() {

    @Override
    public NavigableMap<K, V> descendingMap() {
      return new StandardDescendingMap();
    }

    @Override
    public NavigableSet<K> navigableKeySet() {
      return new StandardNavigableKeySet();
    }

    @Override
    public NavigableSet<K> descendingKeySet() {
      return standardDescendingKeySet();
    }

    @Override
    public K firstKey() {
      return standardFirstKey();

import java.io.Serializable;
import java.util.AbstractSet;
import java.util.Collection;
import java.util.Comparator;
import java.util.Iterator;
import java.util.Map;
import java.util.NavigableMap;
import java.util.NavigableSet;
import java.util.Set;
import java.util.SortedMap;
import java.util.TreeMap;
import org.jspecify.annotations.Nullable;

/**

import com.google.common.testing.SerializableTester;
import java.io.Serializable;
import java.util.Comparator;
import java.util.Map.Entry;
import java.util.NavigableMap;
import java.util.NavigableSet;
import java.util.SortedMap;
import junit.framework.TestSuite;
import org.jspecify.annotations.NullUnmarked;
import org.jspecify.annotations.Nullable;

/**