* @return map of attribute names to values, never {@code null}
     */
    @Nonnull
    Map<String, String> attributes();

    /**
     * Returns the value of a specific attribute.
     *
     * @param name the name of the attribute to retrieve
     * @return the attribute value, or {@code null} if the attribute doesn't exist
     * @throws NullPointerException if name is null
     */
    @Nullable

    String stateString = requestUrl.queryParameter("state");
    ByteString state = stateString != null ? ByteString.decodeBase64(stateString) : null;

    Listener listener;
    synchronized (this) {
      listener = listeners.get(state);
    }

    if (code == null || listener == null) {
      return new MockResponse()
          .setResponseCode(404)
          .setBody("unexpected request");
    }

        }
    }

    public void doCloseContainer() throws Exception {
        if (containerCapsule != null) {
            try {
                containerCapsule.close();
            } finally {
                eventSpyDispatcher = null;
                lookup = null;
                containerCapsule = null;
            }
        }
    }

    public Options options() {
        return options;
    }

   */

  /**
   * Creates a new instance with {@code null} as its detail message and no cause.
   *
   * @deprecated Prefer {@linkplain ExecutionError(Error)} a constructor that accepts a cause: Users
   *     of this class typically expect for instances to have a non-null cause. At the moment, you
   *     can <i>usually</i> still preserve behavior by passing an explicit {@code null} cause. Note,

  private <T extends Iterator<E>> void internalExecuteAndCompare(
      T reference, T target, IteratorOperation method) {
    Object referenceReturnValue = null;
    PermittedMetaException referenceException = null;
    Object targetReturnValue = null;
    Exception targetException = null;

    try {
      targetReturnValue = method.execute(target);
    } catch (Exception e) { // sneaky checked exception
      targetException = e;

    Collection<Entry<K, V>> entries = getSampleEntries(getNumEntries() - 1);
    entries.add(entry(null, v3()));

    resetContainer(getSubjectGenerator().create(entries.toArray()));
    assertTrue(
        "A Map should equal any other Map containing the same entries,"
            + " even if some keys are null.",
        getMap().equals(newHashMap(entries)));
  }

  @CollectionSize.Require(absent = CollectionSize.ZERO)

    @Override
    public File getFile() {
        return path != null ? path.toFile() : null;
    }

    @Override
    public Path getPath() {
        return path;
    }

    @Override
    public void merge(File existing, File result) throws RepositoryException {
        merge(existing != null ? existing.toPath() : null, result != null ? result.toPath() : null);
    }

    @Override

        boolean changed = false;

        if (metadata != null && reference != null) {
            Versioning versioning = metadata.getVersioning();
            Versioning versioningRef = reference.getVersioning();
            if (versioning != null && versioningRef != null) {
                String lastUpdated = versioning.getLastUpdated();

    assertFalse(entries.contains(Maps.<String, @Nullable Boolean>immutableEntry("c", null)));
    assertFalse(entries.contains(Maps.<@Nullable String, Boolean>immutableEntry(null, true)));
  }

  @Override
  public void testKeySetRemoveAllNullFromEmpty() {
    try {
      super.testKeySetRemoveAllNullFromEmpty();
    } catch (RuntimeException tolerated) {

     *
     * @param child The child model, must not be <code>null</code>.
     * @param parent The parent model, may be <code>null</code>.
     * @param childDirectory The directory defined in child model, may be <code>null</code>.
     * @return The path adjustment, can be empty but never <code>null</code>.
     */
    private String getChildPathAdjustment(Model child, Model parent, String childDirectory) {