public Entry<K, V2> lowerEntry(@ParametricNullness K key) {
      return transformEntry(fromMap().lowerEntry(key));
    }

    @Override
    @CheckForNull
    public K lowerKey(@ParametricNullness K key) {
      return fromMap().lowerKey(key);
    }

    @Override
    public NavigableSet<K> navigableKeySet() {
      return fromMap().navigableKeySet();
    }

    @Override
    @CheckForNull

    public Entry<K, V2> lowerEntry(@ParametricNullness K key) {
      return transformEntry(fromMap().lowerEntry(key));
    }

    @Override
    @CheckForNull
    public K lowerKey(@ParametricNullness K key) {
      return fromMap().lowerKey(key);
    }

    @Override
    public NavigableSet<K> navigableKeySet() {
      return fromMap().navigableKeySet();
    }

    @Override
    @CheckForNull