assert data == "Session cookie or query token value is: fakesession"
            data = websocket.receive_text()
            assert data == f"Message text was: {message}, for item ID: foo"
            message = "Message two"
            websocket.send_text(message)
            data = websocket.receive_text()
            assert data == "Session cookie or query token value is: fakesession"
            data = websocket.receive_text()

    ```

So, **FastAPI** will take care of filtering out all the data that is not declared in the output model (using Pydantic).

### `response_model` or Return Type

In this case, because the two models are different, if we annotated the function return type as `UserOut`, the editor and tools would complain that we are returning an invalid type, as those are different classes.

        return data
    ```

    Note that for OAuth2 the scope `items:read` is a single scope in an opaque string.
    You could have custom internal logic to separate it by colon caracters (`:`) or
    similar, and get the two parts `items` and `read`. Many applications do that to
    group and organize permissions, you could do it as well in your application, just
    know that that it is application specific, it's not part of the specification.
    """

    * <a href="https://github.com/swagger-api/swagger-ui" class="external-link" target="_blank">Swagger UI</a>
    * <a href="https://github.com/Rebilly/ReDoc" class="external-link" target="_blank">ReDoc</a>

    These two were chosen for being fairly popular and stable, but doing a quick search, you could find dozens of alternative user interfaces for OpenAPI (that you can use with **FastAPI**).

### Flask REST frameworks

Just keep in mind that when you read "server" in general, it could refer to one of those two things.

When referring to the remote machine, it's common to call it **server**, but also **machine**, **VM** (virtual machine), **node**. Those all refer to some type of remote machine, normally running Linux, where you run programs.

    with client.websocket_connect("/ws/1234") as connection, client.websocket_connect(
        "/ws/5678"
    ) as connection_two:
        connection.send_text("Hello from 1234")
        data1 = connection.receive_text()
        assert data1 == "You wrote: Hello from 1234"
        data2 = connection_two.receive_text()
        client1_says = "Client #1234 says: Hello from 1234"
        assert data2 == client1_says

    with client.websocket_connect("/ws/1234") as connection, client.websocket_connect(
        "/ws/5678"
    ) as connection_two:
        connection.send_text("Hello from 1234")
        data1 = connection.receive_text()
        assert data1 == "You wrote: Hello from 1234"
        data2 = connection_two.receive_text()
        client1_says = "Client #1234 says: Hello from 1234"
        assert data2 == client1_says

                        "content": {
                            "application/json": {



...
```

#### What is OpenAPI for

The OpenAPI schema is what powers the two interactive documentation systems included.

And there are dozens of alternatives, all based on OpenAPI. You could easily add any of those alternatives to your application built with **FastAPI**.

You can continue with the previous instructions for an "Existing Language" for that process.

You can make the first pull request with those two files, `docs/ht/mkdocs.yml` and `docs/ht/index.md`. 🎉

#### Preview the result

As already mentioned above, you can use the `./scripts/docs.py` with the `live` command to preview the results (or `mkdocs serve`).

            assert data == "Session cookie or query token value is: fakesession"
            data = websocket.receive_text()
            assert data == f"Message text was: {message}, for item ID: foo"
            message = "Message two"
            websocket.send_text(message)
            data = websocket.receive_text()
            assert data == "Session cookie or query token value is: fakesession"
            data = websocket.receive_text()