// Fail fast if there's no response queued up.
      return failFastResponse!!
    }

    val result = responseQueue.take()

    // If take() returned because we're shutting down, then enqueue another dead letter so that any
    // other threads waiting on take() will also return.
    if (result == DEAD_LETTER) responseQueue.add(DEAD_LETTER)

    return result
  }

### Create a dependency, or "dependable" { #create-a-dependency-or-dependable }

Let's first focus on the dependency.

It is just a function that can take all the same parameters that a *path operation function* can take:

{* ../../docs_src/dependencies/tutorial001_an_py310.py hl[8:9] *}

That's it.

**2 lines**.

And it has the same shape and structure that all your *path operation functions* have.

Instead of that, by being an "asynchronous" system, once finished, the task can wait in line a little bit (some microseconds) for the computer / program to finish whatever it went to do, and then come back to take the results and continue working with them.

For this, use the Python standard module <a href="https://docs.python.org/3/library/secrets.html" class="external-link" target="_blank">`secrets`</a> to check the username and password.

`secrets.compare_digest()` needs to take `bytes` or a `str` that only contains ASCII characters (the ones in English), this means it wouldn't work with characters like `á`, as in `Sebastián`.

     */
    Source getGlobalToolchainsSource();

    /**
     * Sets the global toolchains source. If both user toolchains and a global toolchains are given, the user toolchains
     * take precedence.
     *
     * @param globalToolchainsSource The global toolchains source, may be {@code null} to disable global toolchains.
     * @return This request, never {@code null}.
     */

                "Minimum supported '$minimumSupported' was not found in available versions: $allVersions"
            }
            val versionsByMinor = allVersions
                .groupBy { it.take(3) } // e.g. 1.9
                .toSortedMap()
            val latests = buildList {
                versionsByMinor.entries.forEachIndexed { idx, entry ->

Here you saw how to use multiple **workers** to **parallelize** the execution of the application, take advantage of **multiple cores** in the CPU, and be able to serve **more requests**.

From the list of deployment concepts from above, using workers would mainly help with the **replication** part, and a little bit with the **restarts**, but you still need to take care of the others:

* **Security - HTTPS**
* **Running on startup**
* ***Restarts***

    // Explicit replacements take priority over unsafe characters.
    builder.addEscape(' ', "_");
    builder.addEscape('!', "_");
    assertThat(builder.build().escape("The Quick Brown Fox!")).isEqualTo("Xhe_Xuick_Xrown_Xox_");
    // Explicit replacements take priority over safe characters.
    builder.setSafeRange(' ', '~');

> The Gradle Build Tool repository is massive, and it will take ages to build on
> a local machine without necessary parallelization and caching.
> The full test suites are executed on the CI instance for multiple configurations,
> and you can rely on it after doing initial sanity check and targeted local testing.

### Copyright and License

When updating/modifying a file, please do not make changes to the copyright header.

### FastAPI Data Filtering { #fastapi-data-filtering }

Now, for FastAPI, it will see the return type and make sure that what you return includes **only** the fields that are declared in the type.