import com.google.common.base.Predicate;
import com.google.common.base.Supplier;
import com.google.common.collect.Maps.IteratorBasedAbstractMap;
import com.google.common.collect.Maps.ViewCachingAbstractMap;
import com.google.common.collect.Sets.ImprovedAbstractSet;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.concurrent.LazyInit;

    return new NavigableAsMapView<>(set, function);
  }

  private static class AsMapView<K extends @Nullable Object, V extends @Nullable Object>
      extends ViewCachingAbstractMap<K, V> {

    private final Set<K> set;
    final Function<? super K, V> function;

    Set<K> backingSet() {
      return set;
    }

    return new NavigableAsMapView<>(set, function);
  }

  private static class AsMapView<K extends @Nullable Object, V extends @Nullable Object>
      extends ViewCachingAbstractMap<K, V> {

    private final Set<K> set;
    final Function<? super K, V> function;

    Set<K> backingSet() {
      return set;
    }