* {@link #tailMap}. If you override {@link #tailMap}, you may wish to override {@link
   * #containsKey} to forward to this implementation.
   *
   * @since 7.0
   */
  @Override
  protected boolean standardContainsKey(@Nullable Object key) {
    try {
      // any CCE or NPE will be caught
      @SuppressWarnings({"unchecked", "nullness"})
      SortedMap<@Nullable Object, V> self = (SortedMap<@Nullable Object, V>) this;

    }

    @Override
    protected NavigableMap<K, V> delegate() {
      return backingMap;
    }

    @Override
    public boolean containsKey(Object key) {
      return standardContainsKey(key);
    }

    @Override
    public boolean containsValue(Object value) {
      return standardContainsValue(value);
    }

    @Override
    public void putAll(Map<? extends K, ? extends V> map) {