swap(array, partitionPoint, i);
        partitionPoint--;
      }
    }

    // We now know that all elements with indexes in (from, partitionPoint] are less than or equal
    // to the pivot at from, and all elements with indexes in (partitionPoint, to] are greater than
    // it. We swap the pivot into partitionPoint and we know the array is partitioned around that.
    swap(array, from, partitionPoint);
    return partitionPoint;

* and from it, import the function `get_token_header`.

That would refer to some package above `app/`, with its own file `__init__.py`, etc. But we don't have that. So, that would throw an error in our example. 🚨

But now you know how it works, so you can use relative imports in your own apps no matter how complex they are. 🤓

### Add some custom `tags`, `responses`, and `dependencies` { #add-some-custom-tags-responses-and-dependencies }

    tests themselves and not the code being tested that needs that access, though there's no
    obvious way to ensure that.

    We could consider arranging things so that only the tests we know need this would get
    the add-opens. Right now that doesn't seem worth the effort, though.
    -->
    <test.add.opens>
      --add-opens java.base/java.lang=ALL-UNNAMED
      --add-opens java.base/java.util=ALL-UNNAMED

    tests themselves and not the code being tested that needs that access, though there's no
    obvious way to ensure that.

    We could consider arranging things so that only the tests we know need this would get
    the add-opens. Right now that doesn't seem worth the effort, though.
    -->
    <test.add.opens>
      --add-opens java.base/java.lang=ALL-UNNAMED
      --add-opens java.base/java.util=ALL-UNNAMED

## Pydantic { #pydantic }

All the data validation is performed under the hood by <a href="https://docs.pydantic.dev/" class="external-link" target="_blank">Pydantic</a>, so you get all the benefits from it. And you know you are in good hands.

You can use the same type declarations with `str`, `float`, `bool` and many other complex data types.

Several of these are explored in the next chapters of the tutorial.

You can create production applications with **FastAPI** right now (and you have probably been doing it for some time), you just have to make sure that you use a version that works correctly with the rest of your code.

## Pin your `fastapi` version { #pin-your-fastapi-version }

The first thing you should do is to "pin" the version of **FastAPI** you are using to the specific latest version that you know works correctly for your application.

      default:
        return new ImmutableEnumSet<>(set);
    }
  }

  /*
   * Notes on EnumSet and <E extends Enum<E>>:
   *
   * This class isn't an arbitrary ForwardingImmutableSet because we need to
   * know that calling {@code clone()} during deserialization will return an
   * object that no one else has a reference to, allowing us to guarantee
   * immutability. Hence, we support only {@link EnumSet}.
   */

        // if we know the size and it fits in an int
        if (size.isPresent() && size.get().longValue() == size.get().intValue()) {
          // otherwise try to presize a StringBuilder
          // it is kind of lame that we need to construct a decoder to access this value.
          // if this is a concern we could add special cases for some known charsets (like utf8)

#*    *##elseif ( $license.name == "CDDL + GPLv2 with classpath exception" )
#*      *##set ( $spdx = 'CDDL+GPLv2-with-classpath-exception' )
#*    *##else
#*      *### unrecognized license will require analysis to know obligations
#*      *##set ( $spdx = $license )
#*    *##end
#*    *###
#*    *### fix project urls that are wrong in pom
#*    *##if ( $project.url.startsWith( "http://www.eclipse.org/sisu/" ) )

    map = MutableClassToInstanceMap.create();
  }

  public void testConstraint() {
    /*
     * We'll give ourselves a pass on testing all the possible ways of breaking the constraint,
     * because we know that newClassMap() is implemented using ConstrainedMap which is itself
     * well-tested. A purist would object to this, but what can I say, we're dirty cheaters.
     */
    map.put(Integer.class, new Integer(5));