/// tip

If you have strict type checks in your editor, mypy, etc, you can declare the function return type as `Any`.

That way you tell the editor that you are intentionally returning anything. But FastAPI will still do the data documentation, validation, filtering, etc. with the `response_model`.

///

### `response_model` Priority { #response-model-priority }

      label: Testgrid link

  - type: textarea
    id: reason
    attributes:
      label: Reason for failure (if possible)

  - type: textarea
    id: additional
    attributes:
      label: Anything else we need to know?

  - type: textarea
    id: sigs
    attributes:
      label: Relevant SIG(s)
      description: You can identify the SIG from the "prowjob_config_url" on the testgrid dashboard for a test.

     */
    public InvokerException(@Nullable String message, @Nullable Throwable cause) {
        super(message, cause);
    }

    /**
     * Exception for intentional exit: No message or anything will be displayed, just the
     * carried exit code will be returned from invoker {@link Invoker#invoke(InvokerRequest)} method.
     */
    public static final class ExitException extends InvokerException {

...then because `description` has a default value, if you **don't return anything** for that field, it will still have that **default value**.

### Model for Output Response Data { #model-for-output-response-data }

If you interact with the docs and check the response, even though the code didn't add anything in one of the `description` fields, the JSON response contains the default value (`null`):

    // Wait for the listeners to be called, don't rely on the same-thread exec.
    listenerLatch.await(5, SECONDS);
    assertTrue(task.isDone());
    assertTrue(task.isCancelled());

    // Make sure we didn't run anything.
    assertEquals(1, runLatch.getCount());
  }

  public void testListenerCalledOnCancelFromRunning() throws Exception {
    exec.execute(task);
    runLatch.await();

  val path = "test.json".toPath()

  fun run() {
    fileSystem.write(path) {
      writeUtf8("{}")
    }

    val request =
      Request
        .Builder()
        .url("https://httpbin.org/anything")
        .put(path.asRequestBody(fileSystem, MEDIA_TYPE_JSON))
        .build()

    client.newCall(request).execute().use { response ->
      if (!response.isSuccessful) throw IOException("Unexpected code $response")

This is different from using an `APIRouter` as a mounted application is completely independent. The OpenAPI and docs from your main application won't include anything from the mounted application, etc.

You can read more about this in the [Advanced User Guide](../advanced/index.md){.internal-link target=_blank}.

## Details { #details }

./mvnw clean install --projects '!guava-testlib,!guava-tests,!guava-bom' -Dmaven.test.skip=true -Dmaven.javadoc.skip=true -f android

# We run this separately so that its change to the default toolchain doesn't affect anything else.
# (And we run it after the main build so that that build has already downloaded Java 11 if necessary.)
./mvnw --projects '!guava-testlib,!guava-tests,!guava-bom,!guava-gwt' initialize -P print-java-11-home

But that's not the only way to declare dependencies (although it would probably be the more common).

The key factor is that a dependency should be a "callable".

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

  // To test this, we give an input where bit 7 is not cleared. For example:
  // (1) 00 01 02 03 04 05 06 07 80
  // (2) 00 01 02 03 04 05 06 07 81
  // (3) 00 01 02 03 04 05 06 07 ff (or anything in between)
  // A fault implementation will generate collisions for these inputs.
  public void testCollisionsDueToIncorrectSignExtension() {