int* num_retvals, ForwardOperation* forward_op_,
                     Tape* tape, const GradientRegistry& registry) {
  TF_RETURN_IF_ERROR(op_->Execute(retvals, num_retvals));
  for (int i = 0; i < *num_retvals; i++) {
    // TODO(srbs): Manage refcount of ForwardOperation's inputs/outputs.
    forward_op_->outputs.push_back(retvals[i]);
  }

   * throttled threads will <b>not</b> be awakened as a result of this invocation, thus they do not
   * observe the new rate; only subsequent requests will.
   *
   * <p>Note though that, since each request repays (by waiting, if necessary) the cost of the
   * <i>previous</i> request, this means that the very next request after an invocation to {@code

    // does not impact recency ordering
    Set<Entry<K, V>> es = entrySet;
    return (es != null) ? es : (entrySet = new EntrySet(this));
  }

  /**
   * Custom Entry class used by EntryIterator.next(), that relays setValue changes to the underlying
   * map.
   */
  private final class WriteThroughEntry implements Entry<K, V> {
    final K key;
    V value;

    WriteThroughEntry(K key, V value) {

import okio.BufferedSink
import okio.BufferedSource
import okio.ByteString
import okio.Sink
import okio.Timeout
import okio.buffer

/**
 * A scriptable web server. Callers supply canned responses and the server replays them upon request
 * in sequence.
 */
public class MockWebServer : Closeable {
  private val taskRunnerBackend =
    TaskRunner.RealBackend(
      threadFactory("MockWebServer TaskRunner", daemon = false),
    )

    @Override
    public V next() {
      return nextEntry().getValue();
    }
  }

  /**
   * Custom Entry class used by EntryIterator.next(), that relays setValue changes to the underlying
   * map.
   */
  final class WriteThroughEntry extends SimpleEntry<K, V> {
    WriteThroughEntry(K key, V value) {
      super(key, value);
    }

    /*

    @Override
    public V next() {
      return nextEntry().getValue();
    }
  }

  /**
   * Custom Entry class used by EntryIterator.next(), that relays setValue changes to the underlying
   * map.
   */
  final class WriteThroughEntry extends SimpleEntry<K, V> {
    WriteThroughEntry(K key, V value) {
      super(key, value);
    }

    /*

    @Override
    public V next() {
      return nextEntry().getValue();
    }
  }

  /**
   * Custom Entry class used by EntryIterator.next(), that relays setValue changes to the underlying
   * map.
   */
  final class WriteThroughEntry implements Entry<K, V> {
    final K key; // non-null
    V value; // non-null

    WriteThroughEntry(K key, V value) {

    @Override
    public V next() {
      return nextEntry().getValue();
    }
  }

  /**
   * Custom Entry class used by EntryIterator.next(), that relays setValue changes to the underlying
   * map.
   */
  final class WriteThroughEntry implements Entry<K, V> {
    final K key; // non-null
    V value; // non-null

    WriteThroughEntry(K key, V value) {