class TracingOperation : public AbstractOperation {
 protected:
  explicit TracingOperation(AbstractOperationKind kind)
      : AbstractOperation(kind) {}

 public:
  // Sets the name of the operation: this is an optional identifier that is
  // not intended to carry semantics and preserved/propagated without
  // guarantees.
  virtual absl::Status SetOpName(const char* op_name) = 0;

  // For LLVM style RTTI.

     *
     * @param tc
     *            context to use
     * @param type2
     *            The Type-2 message which this represents a response to.
     * @param targetName
     *            SPN of the target system, optional
     * @param password
     *            The password to use when constructing the response.
     * @param domain
     *            The domain in which the user has an account.
     * @param user

 * <p>This client requires the following initialization parameters:
 * <ul>
 *   <li>projectId - The Google Cloud project ID</li>
 *   <li>endpoint - Custom endpoint URL (optional, for testing with fake-gcs-server)</li>
 *   <li>credentialsFile - Path to service account JSON file (optional)</li>
 *   <li>connectTimeout - Connection timeout in milliseconds (default: 10000)</li>
 *   <li>writeTimeout - Write timeout in milliseconds (default: 10000)</li>

   * analysis that that means "plain {@code T}" rather than the inferred type {@code @Nullable T}.
   * (And even if annotations on local variables were permitted as an optional hint, no annotation
   * would be the right tool for the job here: {@code @Nullable} is the annotation that we're trying
   * to get rid of, and {@code @NonNull} would be wrong for our use case for the same reason as

import static java.nio.charset.StandardCharsets.UTF_8;
import static org.junit.Assert.assertArrayEquals;
import static org.junit.Assert.assertThrows;

import com.google.common.base.Optional;
import com.google.common.collect.ImmutableList;
import com.google.common.hash.HashCode;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;

* Bridging with Kotlin code is polluted with platform types
* Some public APIs have incorrect nullability annotations (both overly restrictive and overly permissive)

While there are competing ways to represent absence (`Optional`, "Null Object" pattern, method overloads),
it is unlikely that we'll be able to remove `null` entirely.

After migrating to Java 8, we can use pluggable type checkers to ensure that our annotations are consistent, 

  /** Send a pong with the supplied [payload]. */
  @Throws(IOException::class)
  fun writePong(payload: ByteString) {
    writeControlFrame(OPCODE_CONTROL_PONG, payload)
  }

  /**
   * Send a close frame with optional code and reason.
   *
   * @param code Status code as defined by
   *     [Section 7.4 of RFC 6455](http://tools.ietf.org/html/rfc6455#section-7.4) or `0`.
   * @param reason Reason for shutting down or `null`.
   */

     *
     * @return an optional containing the web configuration, or empty if no web URLs were found
     */
    public OptionalEntity<WebConfig> getWebConfig() {
        return OptionalUtil.ofNullable(webConfig);
    }

    /**
     * Gets the file crawling configuration generated from the parsed GSA config.
     *

 *     .weakKeys()
 *     .makeMap();
 * }
 *
 * <p>These features are all optional; {@code new MapMaker().makeMap()} returns a valid concurrent
 * map that behaves similarly to a {@link ConcurrentHashMap}.
 *
 * <p>The returned map is implemented as a hash table with similar performance characteristics to
 * {@link ConcurrentHashMap}. It supports all optional operations of the {@code ConcurrentMap}
 * interface. It does not permit null keys or values.

     * available.
     *
     * @throws InterruptedException if the current thread was interrupted before or during the call
     *     (optional but recommended).
     * @throws CancellationException {@inheritDoc}
     */
    @CanIgnoreReturnValue
    @Override
    public V get(long timeout, TimeUnit unit)