process_after: timedelta = Body(),
    repeat_at: Union[time, None] = Body(default=None),
):
    start_process = start_datetime + process_after
    duration = end_datetime - start_process
    return {
        "item_id": item_id,
        "start_datetime": start_datetime,
        "end_datetime": end_datetime,
        "process_after": process_after,
        "repeat_at": repeat_at,
        "start_process": start_process,

                            "type": "string",
                            "format": "date-time",
                        },
                        "repeat_at": IsDict(
                            {
                                "title": "Repeat At",
                                "anyOf": [
                                    {"type": "string", "format": "time"},
                                    {"type": "null"},

    Because we are using a relative URL, if your API was located at `https://example.com/`, then it would refer to `https://example.com/token`. But if your API was located at `https://example.com/api/v1/`, then it would refer to `https://example.com/api/v1/token`.

* A particular program while it is **running** on the operating system.
    * This doesn't refer to the file, nor to the code, it refers **specifically** to the thing that is being **executed** and managed by the operating system.

* and in there, find the module `dependencies` (the file at `app/dependencies.py`)...
* 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. 🚨

    process_after: Annotated[timedelta, Body()],
    repeat_at: Annotated[time | None, Body()] = None,
):
    start_process = start_datetime + process_after
    duration = end_datetime - start_process
    return {
        "item_id": item_id,
        "start_datetime": start_datetime,
        "end_datetime": end_datetime,
        "process_after": process_after,
        "repeat_at": repeat_at,
        "start_process": start_process,

    process_after: Annotated[timedelta, Body()],
    repeat_at: Annotated[Union[time, None], Body()] = None,
):
    start_process = start_datetime + process_after
    duration = end_datetime - start_process
    return {
        "item_id": item_id,
        "start_datetime": start_datetime,
        "end_datetime": end_datetime,
        "process_after": process_after,
        "repeat_at": repeat_at,
        "start_process": start_process,

Değişkenlerin tiplerini belirterek editör ve araçlardan daha fazla destek alabilirsiniz.

Bu  pythonda tip belirteçleri için **hızlı bir başlangıç / bilgi tazeleme** rehberidir . Bu rehber **FastAPI** kullanmak için gereken minimum konuyu kapsar ki bu da çok az bir miktardır.

**FastAPI' nin** tamamı bu tür tip belirteçleri ile donatılmıştır ve birçok avantaj sağlamaktadır.

We will use this `Base` class we created before to create the SQLAlchemy models.

!!! tip
    SQLAlchemy uses the term "**model**" to refer to these classes and instances that interact with the database.

    But Pydantic also uses the term "**model**" to refer to something different, the data validation, conversion, and documentation classes and instances.

Import `Base` from `database` (the file `database.py` from above).

    ```Python hl_lines="10"
    {!> ../../../docs_src/header_params/tutorial002.py!}
    ```

!!! warning
    Before setting `convert_underscores` to `False`, bear in mind that some HTTP proxies and servers disallow the usage of headers with underscores.

## Duplicate headers

It is possible to receive duplicate headers. That means, the same header with multiple values.