return forward.iterator();
  }

  @Override
  @GwtIncompatible("NavigableSet")
  ImmutableSortedSet<E> createDescendingSet() {
    throw new AssertionError("should never be called");
  }

  @Override
  @CheckForNull
  public E lower(E element) {
    return forward.higher(element);
  }

  @Override
  @CheckForNull
  public E floor(E element) {

                                                  int keep_alive_secs) = 0;

  // Set up a multi-client distributed execution environment. Must be called
  // on all tasks in the cluster. This call internally coordinates with other
  // tasks to initialize the eager context and TF server for multi-client
  // execution.
  virtual absl::Status EnableCollectiveOps(const ServerDef& server_def) = 0;

/**
 * An extension of {@code DataInput} for reading from in-memory byte arrays; its methods offer
 * identical functionality but do not throw {@link IOException}.
 *
 * <p><b>Warning:</b> The caller is responsible for not attempting to read past the end of the
 * array. If any method encounters the end of the array prematurely, it throws {@link

/**
 * Allows core extensions to participate in Maven build session lifecycle.
 *
 * All callback methods (will) follow beforeXXX/afterXXX naming pattern to
 * indicate at what lifecycle point it is being called.
 *
 * @see <a href="https://maven.apache.org/examples/maven-3-lifecycle-extensions.html">example</a>
 * @see <a href="https://issues.apache.org/jira/browse/MNG-4224">MNG-4224</a>
 * @since 3.0-alpha-3
 */

                 TF_Status* out_status) const;

 private:
  // Uses "v2_reader_" to build "var name -> shape" and "var name -> data type"
  // maps; both owned by caller.
  // REQUIRES: "v2_reader_ != nullptr && v2_reader_.status().ok()".
  std::pair<std::unique_ptr<TensorSliceReader::VarToShapeMap>,
            std::unique_ptr<TensorSliceReader::VarToDataTypeMap> >
  BuildV2VarMaps();

}

// Run runs the given function, passing it a stopper channel. If the deadline passes before
// the function finishes executing, Run returns context.DeadlineExceeded to the caller.
// channel so that the work function can attempt to exit gracefully.
// Multiple calls to Run will run independently of each other.
func (d *DeadlineWorker) Run(work func() error) error {

    // (We're relying on callers to call this method only with an edge that's in the graph.)
    return requireNonNull(outEdgeMap.get(edge));
  }

  @Override
  public N removeInEdge(E edge, boolean isSelfLoop) {
    if (isSelfLoop) {
      checkNonNegative(--selfLoopCount);
    }
    N previousNode = inEdgeMap.remove(edge);
    // We're relying on callers to call this method only with an edge that's in the graph.

  }

  /** Throw {@link IllegalStateException} if {@link #createTestSuite()} can't be called yet. */
  protected void checkCanCreate() {
    if (subjectGenerator == null) {
      throw new IllegalStateException("Call using() before createTestSuite().");
    }
    if (name == null) {
      throw new IllegalStateException("Call named() before createTestSuite().");
    }
    if (features == null) {

  }

  /**
   * Map generator that verifies that {@code setUp()} methods are called in all the test cases. The
   * {@code setUpRan} parameter is set true by the {@code setUp} that every test case is supposed to
   * have registered, and set false by the {@code tearDown}. We use a dynamic proxy to intercept all
   * of the {@code Map} method calls and check that {@code setUpRan} is true.
   */

  }

  Stopwatch(Ticker ticker) {
    this.ticker = checkNotNull(ticker, "ticker");
  }

  /**
   * Returns {@code true} if {@link #start()} has been called on this stopwatch, and {@link #stop()}
   * has not been called since the last call to {@code start()}.
   */
  public boolean isRunning() {
    return isRunning;
  }

  /**
   * Starts the stopwatch.
   *