final HashBiMap<K, V> obverse;

    Inverse(HashBiMap<K, V> obverse) {
      this.obverse = obverse;
    }

    @Override
    public int size() {
      return obverse.size;
    }

    @Override
    public boolean containsKey(@Nullable Object key) {
      Object obverseValue = key;
      return obverse.containsValue(obverseValue);
    }

    @Override

        .inOrder();
    // backward map ordered by country
    assertThat(bimap.inverse().keySet())
        .containsExactly(Country.CANADA, Country.CHILE, Country.SWITZERLAND)
        .inOrder();
    // backward map ordered by country (even for currency values)
    assertThat(bimap.inverse().values())
        .containsExactly(Currency.DOLLAR, Currency.PESO, Currency.FRANC)
        .inOrder();
  }

    assertEquals("dollar", bimap.get("canada"));
    assertEquals("canada", bimap.inverse().get("dollar"));
  }

  private static final int N = 1000;

  public void testBashIt() throws Exception {
    BiMap<Integer, Integer> bimap = HashBiMap.create(N);
    BiMap<Integer, Integer> inverse = bimap.inverse();

    for (int i = 0; i < N; i++) {
      assertThat(bimap.put(2 * i, 2 * i + 1)).isNull();
    }

    /* No aliasing on inverse operations. */
    assertSame(unmod.inverse(), unmod.inverse());
    assertSame(unmod, unmod.inverse().inverse());

    /* Unmodifiable is a view. */
    mod.put(4, "four");
    assertEquals(true, unmod.get(4).equals("four"));
    assertEquals(true, unmod.inverse().get("four").equals(4));

        ImmutableListMultimap.<String, Integer>of().inverse());
    assertEquals(ImmutableListMultimap.of(1, "one"), ImmutableListMultimap.of("one", 1).inverse());
    assertEquals(
        ImmutableListMultimap.of(1, "one", 2, "two"),
        ImmutableListMultimap.of("one", 1, "two", 2).inverse());
    assertEquals(
        ImmutableListMultimap.of("of", 'o', "of", 'f', "to", 't', "to", 'o').inverse(),

    assertEquals("{}", bimap.toString());
    assertEquals(HashBiMap.create(), bimap);
    bimap.put(Currency.DOLLAR, "dollar");
    assertEquals("dollar", bimap.get(Currency.DOLLAR));
    assertEquals(Currency.DOLLAR, bimap.inverse().get("dollar"));
  }

  public void testCreateFromMap() {
    /* Test with non-empty Map. */
    Map<Currency, String> map =
        ImmutableMap.of(
            Currency.DOLLAR, "dollar",

    /* No aliasing on inverse operations. */
    assertSame(unmod.inverse(), unmod.inverse());
    assertSame(unmod, unmod.inverse().inverse());

    /* Unmodifiable is a view. */
    mod.put(4, "four");
    assertEquals(true, unmod.get(4).equals("four"));
    assertEquals(true, unmod.inverse().get("four").equals(4));

      super(delegate, predicate);
      this.inverse =
          new FilteredEntryBiMap<>(delegate.inverse(), inversePredicate(predicate), this);
    }

    private FilteredEntryBiMap(
        BiMap<K, V> delegate, Predicate<? super Entry<K, V>> predicate, BiMap<V, K> inverse) {
      super(delegate, predicate);
      this.inverse = inverse;
    }

    BiMap<K, V> unfiltered() {

  public abstract ImmutableCollection<V> get(K key);

  /**
   * Returns an immutable multimap which is the inverse of this one. For every key-value mapping in
   * the original, the result will have a mapping with key and value reversed.
   *
   * @since 11.0
   */
  public abstract ImmutableMultimap<V, K> inverse();

  /**
   * Guaranteed to throw an exception and leave the multimap unmodified.
   *

  public abstract ImmutableCollection<V> get(K key);

  /**
   * Returns an immutable multimap which is the inverse of this one. For every key-value mapping in
   * the original, the result will have a mapping with key and value reversed.
   *
   * @since 11.0
   */
  public abstract ImmutableMultimap<V, K> inverse();

  /**
   * Guaranteed to throw an exception and leave the multimap unmodified.
   *