### Top-level application

First, create the main, top-level, **FastAPI** application, and its *path operations*:

```Python hl_lines="3  6-8"
{!../../../docs_src/sub_applications/tutorial001.py!}
```

### Sub-application

Then, create your sub-application, and its *path operations*.

This sub-application is just another standard FastAPI application, but this is the one that will be "mounted":

The history of **FastAPI** is in great part the history of its predecessors.

As said in the section [Alternatives](alternatives.md){.internal-link target=_blank}:

<blockquote markdown="1">

**FastAPI** wouldn't exist if not for the previous work of others.

There have been many tools created before that have helped inspire its creation.

                <groupId>org.apache.maven.its</groupId>
                <artifactId>bom</artifactId>
                <version>0.1</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <dependencies>
        <dependency>
            <groupId>org.apache.maven.its</groupId>
            <artifactId>a</artifactId>

/**
 * A generator that relies on a preexisting generator for most of its work. For example, a derived
 * iterator generator may delegate the work of creating the underlying collection to an inner
 * collection generator.
 *
 * <p>{@code GwtTestSuiteGenerator} expects every {@code DerivedIterator} implementation to provide
 * a one-arg constructor accepting its inner generator as an argument. This requirement enables it

 *       as that of its keys. This is sometimes called an "invertible map," since the restriction on
 *       values enables it to support an {@linkplain BiMap#inverse inverse view} -- which is another
 *       instance of {@code BiMap}.
 *   <dt>{@link Table}
 *   <dd>A new type, which is similar to {@link java.util.Map}, but which indexes its values by an

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A {@link Multiset} which maintains the ordering of its elements, according to either their
 * natural order or an explicit {@link Comparator}. This order is reflected when iterating over the
 * sorted multiset, either directly, or through its {@code elementSet} or {@code entrySet} views. In

 * <p>
 * It provides information about the file type (or extension) of the associated artifact,
 * its default classifier, and how the artifact will be used in the build when creating
 * class-paths or module-paths.
 * <p>
 * For example, the type {@code java-source} has a {@code jar} extension and a
 * {@code sources} classifier. The artifact and its dependencies should be added
 * to the build path.
 *
 * @since 4.0.0
 */
@Experimental

* If a socket is found, istio-agent will not start its own SDS Server and Envoy will be configured to use that socket as its source of cryptographic material.

Some course providers ✨ [**sponsor FastAPI**](../help-fastapi.md#sponsor-the-author){.internal-link target=_blank} ✨, this ensures the continued and healthy **development** of FastAPI and its **ecosystem**.

And it shows their true commitment to FastAPI and its **community** (you), as they not only want to provide you a **good learning experience** but also want to make sure you have a **good and healthy framework**, FastAPI. 🙇

import java.util.Set;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A bimap (or "bidirectional map") is a map that preserves the uniqueness of its values as well as
 * that of its keys. This constraint enables bimaps to support an "inverse view", which is another
 * bimap containing the same entries as this bimap but with reversed keys and values.
 *
 * <h3>Implementations</h3>
 *