*
 * @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;
    }

  }

  @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() {

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;

/**

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;

/**

      }
    };
  }

  @GwtIncompatible // NavigableSet
  private static <E extends @Nullable Object> NavigableSet<E> removeOnlyNavigableSet(
      NavigableSet<E> set) {
    return new ForwardingNavigableSet<E>() {
      @Override
      protected NavigableSet<E> delegate() {
        return set;
      }

      @Override