To declare those types and the internal types, you can use the standard Python module `typing`. It exists specifically to support these type hints.

#### Newer versions of Python

The syntax using `typing` is **compatible** with all versions, from Python 3.6 to the latest ones, including Python 3.9, Python 3.10, etc.

```

!!! note
    Notice that as we communicate with the database using `await`, the *path operation function* is declared with `async`.

### Notice the `response_model=List[Note]`

It uses `typing.List`.

That documents (and validates, serializes, filters) the output data, as a `list` of `Note`s.

## Create notes

Create the *path operation function* to create notes:

```Python hl_lines="61-65"

    "Topic :: Software Development :: Libraries :: Python Modules",
    "Topic :: Software Development :: Libraries",
    "Topic :: Software Development",
    "Typing :: Typed",
    "Development Status :: 4 - Beta",
    "Environment :: Web Environment",
    "Framework :: AsyncIO",
    "Framework :: FastAPI",
    "Framework :: Pydantic",
    "Framework :: Pydantic :: 1",

## Mounting a **FastAPI** application

"Mounting" means adding a completely "independent" application in a specific path, that then takes care of handling everything under that path, with the _path operations_ declared in that sub-application.

### Top-level application

```console
$ pip install "uvicorn[standard]"

---> 100%
```

</div>

## Példa

### Hozd létre

* Hozz létre a `main.py` fájlt a következő tartalommal:

```Python
from typing import Union

from fastapi import FastAPI

app = FastAPI()


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")

```console
$ pip install "uvicorn[standard]"

---> 100%
```

</div>

## Ejemplo

### Créalo

* Crea un archivo `main.py` con:

```Python
from fastapi import FastAPI
from typing import Union

app = FastAPI()


@app.get("/")
def read_root():
    return {"Hello": "World"}


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

<div class="termy">

```console
$ pip install "uvicorn[standard]"

---> 100%
```

</div>

## উদাহরণ

### তৈরি

- `main.py` নামে একটি ফাইল তৈরি করুন:

```Python
from typing import Union

from fastapi import FastAPI

app = FastAPI()


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")

```

*`resolveDependencies` task resolves dependencies for all platforms including dependencies downloaded by plugins.*

Keep in mind:

- If you’re adding a dependency with OS mentioned in an artifact name (`darwin`, `mac`, `osx`, `linux`, `windows`), remember to add them to 

* Path `prefix`: `/items`.
* `tags`: (just one tag: `items`).
* Extra `responses`.
* `dependencies`: they all need that `X-Token` dependency we created.

So, instead of adding all that to each *path operation*, we can add it to the `APIRouter`.

```Python hl_lines="5-10  16  21" title="app/routers/items.py"
{!../../../docs_src/bigger_applications/app/routers/items.py!}
```

        * Processing a response after being generated by *path operation functions* but before returning it. E.g. adding custom headers, logging, adding extra metadata.
    * New docs section: [Custom Request and APIRoute class](https://fastapi.tiangolo.com/advanced/custom-request-and-route/).