No será serializado con el modelo, etc.

    Asegúrate de que la respuesta tenga los datos que quieras, y que los valores sean JSON válidos (si estás usando `JSONResponse`).

!!! note "Detalles Técnicos"
    También podrías utilizar `from starlette.responses import JSONResponse`.

## Valores predefinidos

Si tienes una *operación de path* que recibe un *parámetro de path* pero quieres que los valores posibles del *parámetro de path* sean predefinidos puedes usar un <abbr title="Enumeration">`Enum`</abbr> estándar de Python.

### Crea una clase `Enum`

Importa `Enum` y crea una sub-clase que herede desde `str` y desde `Enum`.

    * Los validadores también permiten que se definan fácil y claramente schemas complejos de datos. Estos son chequeados y documentados como JSON Schema.
    * Puedes tener objetos de **JSON profundamente anidados** y que todos sean validados y anotados.
* **Extensible**:

If you use a `requirements.txt` file you could specify the version with:

```txt
fastapi==0.45.0
```

that would mean that you would use exactly the version `0.45.0`.

Or you could also pin it with:

```txt
fastapi>=0.45.0,<0.46.0
```

that would mean that you would use the versions `0.45.0` or above, but less than `0.46.0`, for example, a version `0.45.2` would still be accepted.

* **Uvicorn**:
    * Will have the best performance, as it doesn't have much extra code apart from the server itself.

browser("Browser")
proxy["Proxy on http://0.0.0.0:9999/api/v1/app"]
server["Server on http://127.0.0.1:8000/app"]

browser --> proxy
proxy --> server
```

!!! tip
    The IP `0.0.0.0` is commonly used to mean that the program listens on all the IPs available in that machine/server.

The docs UI would also need the OpenAPI schema to declare that this API `server` is located at `/api/v1` (behind the proxy). For example:

This schema definition includes your API paths, the possible parameters they take, etc.

#### Data "schema"

The term "schema" might also refer to the shape of some data, like a JSON content.

In that case, it would mean the JSON attributes, and data types they have, etc.

#### OpenAPI and JSON Schema

It would also mean that if you get data from the `Request` object directly (for example, read the body) it won't be validated, converted or documented (with OpenAPI, for the automatic API user interface) by FastAPI.

!!! tip
    If you know perfectly how imports work, continue to the next section below.

A single dot `.`, like in:

```Python
from .dependencies import get_token_header
```

would mean:

* Starting in the same package that this module (the file `app/routers/items.py`) lives in (the directory `app/routers/`)...
* find the module `dependencies` (an imaginary file at `app/routers/dependencies.py`)...

* The **HTTPS certificates** "certify" a **certain domain**, but the protocol and encryption happen at the TCP level, **before knowing** which domain is being dealt with.
* **By default**, that would mean that you can only have **one HTTPS certificate per IP address**.
    * No matter how big your server is or how small each application you have on it might be.
    * There is a **solution** to this, however.