// Act & Assert
        // unwrap to interface itself should return same instance
        CredentialsInternal unwrapped = creds.unwrap(CredentialsInternal.class);
        assertNotNull(unwrapped, "unwrap to CredentialsInternal returns instance");
        assertSame(creds, unwrapped, "unwrap returns the same object instance");

        // unwrap to unrelated type should return null (use another Credentials implementation)

 * This class holds configuration settings for faceted search including field facets,
 * query facets, and various parameters that control facet behavior.
 */
public class FacetInfo {
    /** Logger instance for this class */
    private static final Logger logger = LogManager.getLogger(FacetInfo.class);

    /** Array of field names to create facets for */
    public String[] field;

    //                                                                           =========
    private static final GroupDbm _instance = new GroupDbm();

    private GroupDbm() {
    }

    public static GroupDbm getInstance() {
        return _instance;
    }

    // ===================================================================================

    List<E> tail = list.subList(1, size);
    assertTrue(copy.contains(list.get(0)));
    assertTrue(head.contains(list.get(0)));
    assertTrue(tail.contains(list.get(1)));
    // The following assumes all elements are distinct.
    assertTrue(copy.contains(list.get(size - 1)));
    assertTrue(head.contains(list.get(size - 2)));
    assertTrue(tail.contains(list.get(size - 1)));
    assertFalse(head.contains(list.get(size - 1)));

    List<E> tail = list.subList(1, size);
    assertTrue(copy.contains(list.get(0)));
    assertTrue(head.contains(list.get(0)));
    assertTrue(tail.contains(list.get(1)));
    // The following assumes all elements are distinct.
    assertTrue(copy.contains(list.get(size - 1)));
    assertTrue(head.contains(list.get(size - 2)));
    assertTrue(tail.contains(list.get(size - 1)));
    assertFalse(head.contains(list.get(size - 1)));

    //                                                                           =========
    private static final DuplicateHostDbm _instance = new DuplicateHostDbm();

    private DuplicateHostDbm() {
    }

    public static DuplicateHostDbm getInstance() {
        return _instance;
    }

    // ===================================================================================

    //                                                                           =========
    private static final RelatedQueryDbm _instance = new RelatedQueryDbm();

    private RelatedQueryDbm() {
    }

    public static RelatedQueryDbm getInstance() {
        return _instance;
    }

    // ===================================================================================

    //                                                                           =========
    private static final RoleTypeDbm _instance = new RoleTypeDbm();

    private RoleTypeDbm() {
    }

    public static RoleTypeDbm getInstance() {
        return _instance;
    }

    // ===================================================================================

   * Returns a new {@code MutableClassToInstanceMap} instance backed by a {@link HashMap} using the
   * default initial capacity and load factor.
   */
  public static <B extends @Nullable Object> MutableClassToInstanceMap<B> create() {
    return new MutableClassToInstanceMap<>(new HashMap<Class<? extends @NonNull B>, B>());
  }

  /**
   * Returns a new {@code MutableClassToInstanceMap} instance backed by a given empty {@code

  /**
   * Returns the empty multimap.
   *
   * <p><b>Performance note:</b> the instance returned is a singleton.
   */
  // Casting is safe because the multimap will never hold any elements.
  @SuppressWarnings("unchecked")
  public static <K, V> ImmutableListMultimap<K, V> of() {
    return (ImmutableListMultimap<K, V>) EmptyImmutableListMultimap.INSTANCE;
  }

  /** Returns an immutable multimap containing a single entry. */