private @Nullable Iterator<? extends Iterator<? extends T>> getTopMetaIterator() {
      while (topMetaIterator == null || !topMetaIterator.hasNext()) {
        if (metaIterators != null && !metaIterators.isEmpty()) {
          topMetaIterator = metaIterators.removeFirst();
        } else {
          return null;
        }
      }
      return topMetaIterator;

        assertEquals(0, response.writeDataWireFormat(null, 0));

        // Read methods return 0 without accessing null buffer
        assertEquals(0, response.readSetupWireFormat(null, 0, 0));
        assertEquals(0, response.readParametersWireFormat(null, 0, 0));
        assertEquals(0, response.readDataWireFormat(null, 0, 0));
    }

    @Test
    @DisplayName("Methods should handle empty buffer")

            logger.warn("Failed to cleanup crawler data: sessionId={}", sessionId, e);
        }
    }

    /**
     * Closes the crawler, releasing resources.
     * This method is called automatically when the crawler is used in a try-with-resources statement.
     */
    @Override
    public void close() {
        clientFactory.close();
    }

    /**

          }

          @Override
          @SuppressWarnings("ThreadPriorityCheck") // doing our best to test for races
          public Boolean get() {
            // Check that this method is called exactly once, by the first
            // thread to synchronize.
            long t0 = System.nanoTime();
            while (waitingThreads() != numThreads - 1) {
              if (System.nanoTime() - t0 > timeout) {

          }

          @Override
          @SuppressWarnings("ThreadPriorityCheck") // doing our best to test for races
          public Boolean get() {
            // Check that this method is called exactly once, by the first
            // thread to synchronize.
            long t0 = System.nanoTime();
            while (waitingThreads() != numThreads - 1) {
              if (System.nanoTime() - t0 > timeout) {

        String result = response.toString();

        // Assert
        assertNotNull(result);
        assertTrue(result.contains("TransPeekNamedPipeResponse"));
        // Verify that parent's toString is called (should contain standard fields)
        assertTrue(result.length() > "TransPeekNamedPipeResponse[]".length());
    }

    @Test
    @DisplayName("Multiple instances should be independent")

    }

    /**
     * Initializes the protocol helper by loading configured protocols from FessConfig
     * and scanning for available protocol handlers in the classpath.
     * This method is called automatically after bean construction.
     */
    @PostConstruct
    public void init() {
        final FessConfig fessConfig = ComponentUtil.getFessConfig();

    if (expectedSequenceNumber != ANY_SEQUENCE_NUMBER &&
      (entry == null || entry.sequenceNumber != expectedSequenceNumber)
    ) {
      return null // Snapshot is stale.
    }

    if (entry?.currentEditor != null) {
      return null // Another edit is in progress.
    }

    if (entry != null && entry.lockingSourceCount != 0) {
      return null // We can't write this file because a reader is still reading it.
    }

     *     {@code lock}, or {@code null} if no path was found.
     */
    private @Nullable ExampleStackTrace findPathTo(LockGraphNode node, Set<LockGraphNode> seen) {
      if (!seen.add(this)) {
        return null; // Already traversed this node.
      }
      ExampleStackTrace found = allowedPriorLocks.get(node);
      if (found != null) {
        return found; // Found a path ending at the node!

     *     is null. The builder is left in an invalid state.
     */
    @CanIgnoreReturnValue
    public Builder<K, V> putAll(K key, Iterable<? extends V> values) {
      if (key == null) {
        throw new NullPointerException("null key in entry: null=" + Iterables.toString(values));
      }
      Iterator<? extends V> valuesItr = values.iterator();