Files.createDirectories(userConf);
        Path userExtensions = userConf.resolve("settings.xml");
        Files.writeString(userExtensions, settingsXml);

        // we just execute a Mojo for downloading it only and to assert from which URL it came
        Map<String, String> logs = invoke(
                cwd,
                userHome,

A "**callable**" in Python is anything that Python can "call" like a function.

So, if you have an object `something` (that might _not_ be a function) and you can "call" it (execute it) like:

```Python
something()
```

or

```Python
something(some_argument, some_keyword_argument="foo")
```

then it is a "callable".

        final SearchRequestBuilder builder = client.prepareSearch(index);
        builder.setSize(size);
        builder.setQuery(buildQuery());
        builder.setRescorer(buildRescore(), windowSize);

        builder.execute(new ActionListener<SearchResponse>() {
            @Override
            public void onResponse(final SearchResponse searchResponse) {
                if (searchResponse.getFailedShards() > 0) {

        // Prepare test data
        byte[] sourceData = { 10, 20, 30, 40, 50 };
        byte[] buffer = new byte[100];
        System.arraycopy(sourceData, 0, buffer, 10, sourceData.length);

        // Execute
        int result = response.readDataWireFormat(buffer, 10, sourceData.length);

        // Verify
        assertEquals(sourceData.length, result);
        // Check that data was copied to output buffer

    if (TF_GetCode(s) != TF_OK) {
      return;
    }
  }
  int num_outputs = unwrap(o)->expected_num_outputs;
  tsl::Set_TF_Status_from_Status(
      s, unwrap(op)->Execute(
             absl::MakeSpan(reinterpret_cast<AbstractTensorHandle**>(
                                unwrap(o)->outputs.data()),
                            unwrap(o)->outputs.size()),
             &num_outputs));
}

        final AtomicInteger counter = new AtomicInteger(0);
        final ForkJoinPool pool = new ForkJoinPool(10);
        for (int i = 0; i < 1000; i++) {
            pool.execute(() -> {
                assertEquals(result, crawlingInfoHelper.generateId(dataMap));
                counter.incrementAndGet();
            });
        }
        pool.shutdown();

You don't even have to check if the token exists to return an error. You can be sure that if your function is executed, it will have a `str` in that token.

You can try it already in the interactive docs:

<img src="/img/tutorial/security/image03.png">

We are not verifying the validity of the token yet, but that's a start already.

  // Block until all pending nodes are finished.
  virtual absl::Status AsyncWait() = 0;

  // Add a function (serialized FunctionDef protocol buffer) so that it can
  // be executed as an op. Return error if the function with the same name
  // already exists.
  virtual absl::Status AddFunctionDef(const FunctionDef& fdef) = 0;

  // Notifies about the function removal.

                stream(baseExcludes).of(stream -> stream.forEach(exclude -> popularWordsRequestBuilder.addExcludeWord(exclude)));
                try {
                    popularWordsRequestBuilder.execute().getResponse().getItems().stream().forEach(item -> wordList.add(item.getText()));
                } catch (final SuggesterException e) {
                    logger.warn("Failed to generate popular words.", e);
                }

        String stats = null;
        try {
            final SearchEngineClient esClient = ComponentUtil.getSearchEngineClient();
            final NodesStatsResponse response = esClient.admin().cluster().prepareNodesStats().all().execute().actionGet(10000L);
            final XContentBuilder builder = XContentFactory.jsonBuilder();
            builder.startObject();
            response.toXContent(builder, ToXContent.EMPTY_PARAMS);