* @throws NullPointerException if any key or value in {@code map} is null
   */
  public static <K, V> ImmutableBiMap<K, V> copyOf(Map<? extends K, ? extends V> map) {
    if (map instanceof ImmutableBiMap) {
      @SuppressWarnings("unchecked") // safe since map is not writable
      ImmutableBiMap<K, V> bimap = (ImmutableBiMap<K, V>) map;
      // TODO(lowasser): if we need to make a copy of a BiMap because the

  }

  public void testOf() {
    assertMapEquals(ImmutableBiMap.of("one", 1), "one", 1);
    assertMapEquals(ImmutableBiMap.of("one", 1).inverse(), 1, "one");
    assertMapEquals(ImmutableBiMap.of("one", 1, "two", 2), "one", 1, "two", 2);
    assertMapEquals(ImmutableBiMap.of("one", 1, "two", 2).inverse(), 1, "one", 2, "two");
    assertMapEquals(
        ImmutableBiMap.of("one", 1, "two", 2, "three", 3), "one", 1, "two", 2, "three", 3);

          }
        }
        return ImmutableBiMap.copyOf(sourceMap);
      }
    },
    COPY_OF_ENTRIES {
      @Override
      public ImmutableBiMap<Object, Object> create(List<Entry<?, ?>> entries) {
        return ImmutableBiMap.copyOf(entries);
      }
    },
    BUILDER_PUT_ONE_BY_ONE {
      @Override
      public ImmutableBiMap<Object, Object> create(List<Entry<?, ?>> entries) {

        return HashBiMap.create(map);
      }
    },
    ImmutableBiMapImpl {
      @Override
      public <K extends Comparable<K>, V> BiMap<K, V> create(Map<K, V> map) {
        return ImmutableBiMap.copyOf(map);
      }
    };

    @Override
    public abstract <K extends Comparable<K>, V> BiMap<K, V> create(Map<K, V> map);
  }

  enum MultisetImpl implements CollectionsImplEnum {

        return HashBiMap.create(map);
      }
    },
    ImmutableBiMapImpl {
      @Override
      public <K extends Comparable<K>, V> BiMap<K, V> create(Map<K, V> map) {
        return ImmutableBiMap.copyOf(map);
      }
    };

    @Override
    public abstract <K extends Comparable<K>, V> BiMap<K, V> create(Map<K, V> map);
  }

  enum MultisetImpl implements CollectionsImplEnum {

   * mainly for consistency and maintainability of your code.
   */
  public static <K, V> ImmutableMap<K, V> of(K k1, V v1) {
    return ImmutableBiMap.of(k1, v1);
  }

  /**
   * Returns an immutable map containing the given entries, in order.
   *
   * @throws IllegalArgumentException if duplicate keys are provided
   */

  }

  static <K extends @Nullable Object, V extends @Nullable Object> BiMap<K, V> biMap(
      BiMap<K, V> bimap, @CheckForNull Object mutex) {
    if (bimap instanceof SynchronizedBiMap || bimap instanceof ImmutableBiMap) {
      return bimap;
    }
    return new SynchronizedBiMap<>(bimap, mutex, null);
  }

  static final class SynchronizedBiMap<K extends @Nullable Object, V extends @Nullable Object>

  }

  static <K extends @Nullable Object, V extends @Nullable Object> BiMap<K, V> biMap(
      BiMap<K, V> bimap, @CheckForNull Object mutex) {
    if (bimap instanceof SynchronizedBiMap || bimap instanceof ImmutableBiMap) {
      return bimap;
    }
    return new SynchronizedBiMap<>(bimap, mutex, null);
  }

  static final class SynchronizedBiMap<K extends @Nullable Object, V extends @Nullable Object>