This client could be a browser with a frontend, a code from someone else, an IoT device, etc.

You could need to tell the client that:

* The client doesn't have enough privileges for that operation.
* The client doesn't have access to that resource.
* The item the client was trying to access doesn't exist.
* etc.

# OpenAPI Callbacks

You could create an API with a *path operation* that could trigger a request to an *external API* created by someone else (probably the same developer that would be *using* your API).

     *
     * @param request the dependency collection request, must not be {@code null}
     * @return the collection result, never {@code null}
     * @throws DependencyCollectorException if the dependency tree could not be built
     * @throws IllegalArgumentException if an argument is null or invalid
     *
     * @see DependencyCollector#collect(Session, Project)
     * @see DependencyCollector#collect(Session, DependencyCoordinate)

errors.design_editor_disabled=This feature is disabled.
errors.not_found_on_file_system=Not Found: {0}
errors.could_not_open_on_system=Could not open {0}. <br/>Please check if the file is associated with an application.
errors.result_size_exceeded=No more results could be displayed.
errors.target_file_does_not_exist={0} file does not exist.
errors.failed_to_delete_file=Failed to delete {0} file.

                                                       askance--
Said he thanked the whiting kindly, but he would not join the
   dance.
    Would not, could not, would not, could not, would not join
        the dance.
    Would not, could not, would not, could not, could not join
        the dance.

`"What matters it how far we go?" his scaly friend replied.

     *
     * @param originatingArtifact the artifact that was being resolved
     * @param resolvedArtifacts   artifacts that could be resolved
     * @param missingArtifacts    artifacts that could not be resolved
     * @param remoteRepositories  remote repositories where the missing artifacts were not found
     */
    public MultipleArtifactsNotFoundException(

<img src="/img/tutorial/extending-openapi/image03.png">

## Change the Theme

The same way you could set the syntax highlighting theme with the key `"syntaxHighlight.theme"` (notice that it has a dot in the middle):

```Python hl_lines="3"
{!../../../docs_src/configure_swagger_ui/tutorial002.py!}
```

That configuration would change the syntax highlighting color theme:

<img src="/img/tutorial/extending-openapi/image04.png">

This Manager Process would probably be the one listening on the **port** in the IP. And it would transmit all the communication to the worker processes.

Those worker processes would be the ones running your application, they would perform the main computations to receive a **request** and return a **response**, and they would load anything you put in variables in RAM.

            final InputStreamThread ist = jobProcess.getInputStreamThread();
            try {
                ist.interrupt();
            } catch (final Exception e) {
                logger.warn("Could not interrupt a thread of an input stream.", e);
            }

            final CountDownLatch latch = new CountDownLatch(3);
            final Process process = jobProcess.getProcess();
            new Thread(() -> {

And then, you could give that JWT token to a user (or bot), and they could use it to perform those actions (drive the car, or edit the blog post) without even needing to have an account, just with the JWT token your API generated for that.

Using these ideas, JWT can be used for way more sophisticated scenarios.

In those cases, several of those entities could have the same ID, let's say `foo` (a user `foo`, a car `foo`, and a blog post `foo`).