if (o instanceof Entry) {
          Entry<?, ?> entry = (Entry<?, ?>) o;
          return containsMapping(entry.getKey(), columnKey, entry.getValue());
        }
        return false;
      }

      @Override
      public boolean remove(@CheckForNull Object obj) {
        if (obj instanceof Entry) {
          Entry<?, ?> entry = (Entry<?, ?>) obj;

    @SuppressWarnings("unchecked")
    Entry<String, String>[] array = (Entry<String, String>[]) new Entry<?, ?>[entries.length];
    int i = 0;
    for (Object o : entries) {
      @SuppressWarnings("unchecked")
      Entry<String, String> e = (Entry<String, String>) o;
      array[i++] = e;
    }
    return create(array);
  }

  protected abstract Map<String, String> create(Entry<String, String>[] entries);

  @Override

    @SuppressWarnings("unchecked")
    Entry<String, String>[] array = (Entry<String, String>[]) new Entry<?, ?>[entries.length];
    int i = 0;
    for (Object o : entries) {
      @SuppressWarnings("unchecked")
      Entry<String, String> e = (Entry<String, String>) o;
      array[i++] = e;
    }
    return create(array);
  }

  protected abstract Map<String, String> create(Entry<String, String>[] entries);

  @Override

          reverse(samples.e3()),
          reverse(samples.e4()));
    }

    private Entry<V, K> reverse(Entry<K, V> entry) {
      return Helpers.mapEntry(entry.getValue(), entry.getKey());
    }

    @SuppressWarnings("unchecked")
    @Override
    public BiMap<V, K> create(Object... elements) {
      Entry<?, ?>[] entries = new Entry<?, ?>[elements.length];
      for (int i = 0; i < elements.length; i++) {

                  @Override
                  protected SortedMap<String, String> create(Entry<String, String>[] entries) {
                    SortedMap<String, String> map = new SafeTreeMap<>();
                    for (Entry<String, String> entry : entries) {
                      map.put(entry.getKey(), entry.getValue());
                    }
                    return new StandardImplForwardingSortedMap<>(map);

  }

  public void testToString() {
    assertEquals("foo=1", entry("foo", 1).toString());
  }

  public void testToStringNull() {
    assertEquals("null=1", entry(NK, 1).toString());
    assertEquals("foo=null", entry("foo", NV).toString());
    assertEquals("null=null", entry(NK, NV).toString());
  }

  public void testEquals() {
    Entry<String, Integer> foo1 = entry("foo", 1);

  @Override
  public Set<Entry<K, V>> create(Object... elements) {
    Entry<K, V>[] entries = createArray(elements.length);
    System.arraycopy(elements, 0, entries, 0, elements.length);
    return createFromEntries(entries);
  }

  public abstract Set<Entry<K, V>> createFromEntries(Entry<K, V>[] entries);

  @Override
  @SuppressWarnings("unchecked") // generic arrays make typesafety sad
  public Entry<K, V>[] createArray(int length) {

  static <K extends @Nullable Object, V extends @Nullable Object> Entry<V, K> reverseEntry(
      Entry<K, V> entry) {
    return Helpers.mapEntry(entry.getValue(), entry.getKey());
  }

  @Override
  protected void expectContents(Collection<Entry<K, V>> expected) {
    super.expectContents(expected);
    List<Entry<V, K>> reversedEntries = new ArrayList<>();
    for (Entry<K, V> entry : expected) {
      reversedEntries.add(reverseEntry(entry));

  static <K extends @Nullable Object, V extends @Nullable Object> Entry<V, K> reverseEntry(
      Entry<K, V> entry) {
    return Helpers.mapEntry(entry.getValue(), entry.getKey());
  }

  @Override
  protected void expectContents(Collection<Entry<K, V>> expected) {
    super.expectContents(expected);
    List<Entry<V, K>> reversedEntries = new ArrayList<>();
    for (Entry<K, V> entry : expected) {
      reversedEntries.add(reverseEntry(entry));

  protected Entry<K, V> standardLastEntry() {
    return Iterables.<@Nullable Entry<K, V>>getFirst(descendingMap().entrySet(), null);
  }

  /**
   * A sensible definition of {@link #lastKey} in terms of {@code lastEntry}. If you override {@code
   * lastEntry}, you may wish to override {@code lastKey} to forward to this implementation.
   */
  protected K standardLastKey() {
    Entry<K, V> entry = lastEntry();
    if (entry == null) {