# Using Dataclasses

FastAPI is built on top of **Pydantic**, and I have been showing you how to use Pydantic models to declare requests and responses.

But FastAPI also supports using <a href="https://docs.python.org/3/library/dataclasses.html" class="external-link" target="_blank">`dataclasses`</a> the same way:

{* ../../docs_src/dataclasses/tutorial001.py hl[1,7:12,19:20] *}

# Envoy binary variables
ISTIO_ENVOY_BASE_URL="${ISTIO_ENVOY_BASE_URL:-https://storage.googleapis.com/istio-build/proxy}"

# If we are not using the default, assume its private and we need to authenticate
if [[ "${ISTIO_ENVOY_BASE_URL}" != "https://storage.googleapis.com/istio-build/proxy" ]]; then
  AUTH_HEADER="Authorization: Bearer $(gcloud auth print-access-token)"
  export AUTH_HEADER
fi

    }

    /**
     * Sets the concurrency level that will be used by the to-be-built {@link Interner}.
     *
     * @see MapMaker#concurrencyLevel(int)
     */
    public InternerBuilder concurrencyLevel(int concurrencyLevel) {
      this.mapMaker.concurrencyLevel(concurrencyLevel);
      return this;
    }

    public <E> Interner<E> build() {
      if (!strong) {
        mapMaker.weakKeys();
      }

* API keys in:
    * Headers.
    * Query parameters.
    * Cookies, etc.

Plus all the security features from Starlette (including **session cookies**).

All built as reusable tools and components that are easy to integrate with your systems, data stores, relational and NoSQL databases, etc.

### Dependency Injection

 * [Coil](https://github.com/coil-kt/coil): An image loading library for Android backed by Kotlin Coroutines.
 * [Communicator](https://github.com/Taig/Communicator): An OkHttp wrapper for Scala built with Android in mind.
 * [Cronet Transport for OkHttp](https://github.com/google/cronet-transport-for-okhttp): A HTTP3 ready transport layer for OkHttp on Android, based on Chromium network stack.

To do that, first build all the docs:

<div class="termy">

```console
// Use the command "build-all", this will take a bit
$ python ./scripts/docs.py build-all

Building docs for: en
Building docs for: es
Successfully built docs for: es
```

</div>

# the CACHEBUSTER to the PR number.
build --action_env=CACHEBUSTER=20220325

# Use Python 3.X as installed in container image
build --action_env PYTHON_BIN_PATH="/usr/local/bin/python3"
build --python_path="/usr/local/bin/python3"

# Build TensorFlow v2
build --define=tf_api_version=2 --action_env=TF2_BEHAVIOR=1

# Use lld as the linker
build --linkopt="-fuse-ld=lld"
build --linkopt="-lm"

		result *= 7
	}()
	return 6
}
</pre>

<h2 id="Built-in_functions">Built-in functions</h2>

<p>
Built-in functions are
<a href="#Predeclared_identifiers">predeclared</a>.
They are called like any other function but some of them
accept a type instead of an expression as the first argument.
</p>

<p>
The built-in functions do not have standard Go types,

✋️ 🕐 👆 🔨, 👆 💪 💯 ⚫️ 🌐 ⚫️ 🔜 👀 💳.

👈, 🥇 🏗 🌐 🩺:

<div class="termy">

```console
// Use the command "build-all", this will take a bit
$ python ./scripts/docs.py build-all

Updating es
Updating en
Building docs for: en
Building docs for: es
Successfully built docs for: es
Copying en index.md to README.md
```

</div>

    }

    /**
     * Sets the concurrency level that will be used by the to-be-built {@link Interner}.
     *
     * @see MapMaker#concurrencyLevel(int)
     */
    public InternerBuilder concurrencyLevel(int concurrencyLevel) {
      this.mapMaker.concurrencyLevel(concurrencyLevel);
      return this;
    }

    public <E> Interner<E> build() {
      if (!strong) {
        mapMaker.weakKeys();
      }