//
            // If we were to cancel taskFuture, that would let the next task start while the old
            // one is still running.
            //
            // Now, maybe we could tweak our implementation to not start the next task until the
            // callable actually completes. (We could detect completion in our wrapper
            // `AsyncCallable task`.) However, our contract also promises:

For example, it doesn't receive `datetime` objects, as those are not compatible with JSON.

So, a `datetime` object would have to be converted to a `str` containing the data in <a href="https://en.wikipedia.org/wiki/ISO_8601" class="external-link" target="_blank">ISO format</a>.

The same way, this database wouldn't receive a Pydantic model (an object with attributes), only a `dict`.

You can use `jsonable_encoder` for that.

```Python hl_lines="1  4"
{!> ../../docs_src/python_types/tutorial008b_py39.py!}
```

////

In both cases this means that `item` could be an `int` or a `str`.

#### Possibly `None` { #possibly-none }

You can declare that a value could have a type, like `str`, but that it could also be `None`.

In Python 3.6 and above (including Python 3.10) you can declare it by importing and using `Optional` from the `typing` module.

  // in the short hash. We saw that a mask of 0x7f would keep the 7-bit value 0x6f from a full
  // hashcode of 0x89abcdef. The imaginary `hash` value would then be the remaining top 25 bits,
  // 0x89abcd80. To this is added (or'd) the `next` value, which is an index within `entries`
  // (and therefore within `keys` and `values`) of another entry that has the same short hash

```Python
{"id": id}
```

For example, with an ID of `42`, this would render:

```html
Item ID: 42
```

### Template `url_for` Arguments { #template-url-for-arguments }

You can also use `url_for()` inside of the template, it takes as arguments the same arguments that would be used by your *path operation function*.

So, the section with:

{% raw %}

```jinja

<img src="/img/tutorial/extending-openapi/image03.png">

## Change the Theme { #change-the-theme }

The same way you could set the syntax highlighting theme with the key `"syntaxHighlight.theme"` (notice that it has a dot in the middle):

{* ../../docs_src/configure_swagger_ui/tutorial002_py39.py hl[3] *}

That configuration would change the syntax highlighting color theme:

<img src="/img/tutorial/extending-openapi/image04.png">

So, you could add additional data to the automatically generated schema.

For example, you could decide to read and validate the request with your own code, without using the automatic features of FastAPI with Pydantic, but you could still want to define the request in the OpenAPI schema.

You could do that with `openapi_extra`:

     *
     * - Any kind of Error from a listener. Even if we could distinguish that case (by exposing some
     * extra state from AbstractFuture), our options are limited: A call to setException() would be
     * a no-op. We could log, but if that's what we really want, we should modify
     * AbstractFuture.executeListener to do so, since that method would have the ability to continue
     * to execute other listeners.
     *

* **`200 - 299`** are for "Successful" responses. These are the ones you would use the most.
    * `200` is the default status code, which means everything was "OK".
    * Another example would be `201`, "Created". It is commonly used after creating a new record in the database.

 * a file or directory that would be more accessible.
 */
@J2ktIncompatible
@GwtIncompatible
@J2ObjCIncompatible
abstract class TempFileCreator {
  static final TempFileCreator INSTANCE = pickSecureCreator();

  /**
   * @throws IllegalStateException if the directory could not be created (to implement the contract