They are more relevant for older versions, before OpenAPI 3.1.0 was available.

    You can consider this a brief OpenAPI and JSON Schema **history lesson**. 🤓

!!! warning
    These are very technical details about the standards **JSON Schema** and **OpenAPI**.

    If the ideas above already work for you, that might be enough, and you probably don't need these details, feel free to skip them.

<div class="termy">

```console
// Используйте команду "serve" после того, как отработает команда "build-all"
$ python ./scripts/docs.py serve

Warning: this is a very simple server. For development, use mkdocs serve instead.
This is here only to preview a site with translations already built.
Make sure you run the build-all command first.
Serving at: http://127.0.0.1:8008
```

    ```Python hl_lines="1  4"
    {!> ../../../docs_src/python_types/tutorial009b.py!}
    ```

#### Sử dụng `Union` hay `Optional`

If you are using a Python version below 3.10, here's a tip from my very **subjective** point of view:

Nếu bạn đang sử dụng phiên bản Python dưới 3.10, đây là một mẹo từ ý kiến rất "chủ quan" của tôi:

* 🚨 Tránh sử dụng `Optional[SomeType]`