return {"Hello": "World"}


@app.get("/items/{item_id}")
async def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}
```

**Note**:

If you don't know, check the _"In a hurry?"_ section about <a href="https://fastapi.tiangolo.com/async/#in-a-hurry" target="_blank">`async` and `await` in the docs</a>.

</details>

### Run it { #run-it }

Run the server with:

## Épinglez votre version de `fastapi`

Tout d'abord il faut "épingler" la version de **FastAPI** que vous utilisez à la dernière version dont vous savez
qu'elle fonctionne correctement pour votre application.

Par exemple, disons que vous utilisez la version `0.45.0` dans votre application.

 *
 * This class ensures that at most one thread is running at a time. This is initially the JUnit test
 * thread, which yields its execution privilege while calling [runTasks], [runNextTask], or
 * [advanceUntil]. These functions don't return until the task threads are all idle.
 *
 * Task threads release their execution privilege in these ways:
 *
 *  * By yielding in [TaskRunner.Backend.coordinatorWait].
 *  * By yielding in [BlockingQueue.poll].

    override fun coordinatorNotify(taskRunner: TaskRunner) {
      taskRunner.notify()
    }

    /**
     * Wait a duration in nanoseconds. Unlike [java.lang.Object.wait] this interprets 0 as
     * "don't wait" instead of "wait forever".
     */
    @Throws(InterruptedException::class)
    @Suppress("PLATFORM_CLASS_MAPPED_TO_KOTLIN")
    override fun coordinatorWait(
      taskRunner: TaskRunner,
      nanos: Long,

    // below the values of characters in surrogate pairs, this cannot occur.
    // This approach does mean that we break out of the fast path code in cases
    // where we don't strictly need to, but this situation will almost never
    // occur in practice.
    if (safeMin >= Character.MIN_HIGH_SURROGATE) {
      // The safe range is empty or the all safe code points lie in or above the

    return new LinearTransformationBuilder(x1, y1);
  }

  /**
   * This is an intermediate stage in the construction process. It is returned by {@link
   * LinearTransformation#mapping}. You almost certainly don't want to keep instances around, but
   * instead use method chaining. This represents a single point mapping, i.e. a mapping between one
   * {@code x} and {@code y} value pair.
   *
   * @since 20.0
   */

                        } else {
                            result = -1;
                        }
                    }
                    if (result == 0) {
                        // We don't consider the version range in the comparison, just the resolved version
                        result = new DefaultArtifactVersion(version)
                                .compareTo(new DefaultArtifactVersion(a.getVersion()));

Define a file parameter with a type of `UploadFile`:

{* ../../docs_src/request_files/tutorial001_an_py39.py hl[14] *}

Using `UploadFile` has several advantages over `bytes`:

* You don't have to use `File()` in the default value of the parameter.
* It uses a "spooled" file:
    * A file stored in memory up to a maximum size limit, and after passing this limit it will be stored in disk.

    assertEquals((Integer) 5, converter.convert("5"));
    assertEquals("5", converter.reverse().convert(5));
  }

  // Null-passthrough violates our nullness annotations, so we don't support it under J2KT.
  @J2ktIncompatible
  public void testNullIsPassedThrough() {
    Converter<String, String> nullsArePassed = sillyConverter(false);
    assertEquals("forward", nullsArePassed.convert("foo"));

    }

    @Override
    public E element() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.element();
    }

    @Override
    public Iterator<E> iterator() {
      // We explicitly don't lock for iterator()
      assertFalse(Thread.holdsLock(mutex));
      return delegate.iterator();
    }

    @Override
    public int size() {
      assertTrue(Thread.holdsLock(mutex));