Dans les versions précédentes de Javascript NodeJS / Navigateur, vous auriez utilisé des "callbacks". Menant potentiellement à ce que l'on appelle <a href="http://callbackhell.com/" class="external-link" target="_blank">le "callback hell"</a>.


## Coroutines

But in this case, if you could bring the 8 ex-cashier/cooks/now-cleaners, and each one of them (plus you) could take a zone of the house to clean it, you could do all the work in **parallel**, with the extra help, and finish much sooner.

In this scenario, each one of the cleaners (including you) would be a processor, doing their part of the job.

    These Pydantic models define more or less a "schema" (a valid data shape).

    So this will help us avoiding confusion while using both.

### Create the Pydantic *models* / schemas

Create all the same Pydantic models as in the SQLAlchemy tutorial:

```Python hl_lines="16-18  21-22  25-30  34-35  38-39  42-48"

    These Pydantic models define more or less a "schema" (a valid data shape).

    So this will help us avoiding confusion while using both.

### Create initial Pydantic *models* / schemas

Create an `ItemBase` and `UserBase` Pydantic *models* (or let's say "schemas") to have common attributes while creating or reading data.

from fastapi import FastAPI

description = """
ChimichangApp API helps you do awesome stuff. 🚀

## Items

You can **read items**.

## Users

You will be able to:

* **Create users** (_not implemented_).
* **Read users** (_not implemented_).
"""

app = FastAPI(
    title="ChimichangApp",
    description=description,
    summary="Deadpool's favorite app. Nuff said.",
    version="0.0.1",

                ```python
                from fastapi import FastAPI

                app = FastAPI(
                    description="""
                                ChimichangApp API helps you do awesome stuff. 🚀

                                ## Items

                                You can **read items**.

                                ## Users

    assert response.json() == {
        "openapi": "3.1.0",
        "info": {
            "title": "ChimichangApp",
            "summary": "Deadpool's favorite app. Nuff said.",
            "description": "\nChimichangApp API helps you do awesome stuff. 🚀\n\n## Items\n\nYou can **read items**.\n\n## Users\n\nYou will be able to:\n\n* **Create users** (_not implemented_).\n* **Read users** (_not implemented_).\n",

En versiones anteriores de NodeJS / Browser JavaScript, habrías utilizado "callbacks". Lo que conduce a <a href="http://callbackhell.com/" class="external-link" target="_blank">callback hell</a>.

## Coroutines