{* ../../docs_src/behind_a_proxy/tutorial002_py39.py hl[3] *}

Passing the `root_path` to `FastAPI` would be the equivalent of passing the `--root-path` command line option to Uvicorn or Hypercorn.

### About `root_path` { #about-root-path }

Keep in mind that the server (Uvicorn) won't use that `root_path` for anything else than passing it to the app.

UserInDB(**user_dict)
```

would be equivalent to:

```Python
UserInDB(**user_in.model_dump())
```

...because `user_in.model_dump()` is a `dict`, and then we make Python "unpack" it by passing it to `UserInDB` prefixed with `**`.

So, we get a Pydantic model from the data in another Pydantic model.

#### Unpacking a `dict` and extra keywords { #unpacking-a-dict-and-extra-keywords }

):
    # This is an incorrect way of using it, this is not checking if the scopes are
    # provided by the token, only if the endpoint is requesting them, but the test
    # here is just to check if FastAPI is indeed registering and passing the scopes
    # correctly when using Security with parameterless dependencies.
    if "a" not in security_scopes.scopes or "b" not in security_scopes.scopes:

		if _, err := uuid.Parse(vid); err != nil {
			return opts, InvalidVersionID{
				Bucket:    bucket,
				Object:    object,
				VersionID: vid,
			}
		}
	}

	// default case of passing encryption headers to backend
	opts, err = getDefaultOpts(r.Header, false, nil)
	if err != nil {
		return opts, err
	}
	opts.PartNumber = partNumber
	opts.VersionID = vid

For those cases, you can use the `jsonable_encoder` to convert your data before passing it to a response:

{* ../../docs_src/response_directly/tutorial001_py310.py hl[5:6,20:21] *}

/// note | Technical Details

You could also use `from starlette.responses import JSONResponse`.

<img src="/img/tutorial/path-operation-configuration/image05.png">

## Recap { #recap }

///

The only thing the function returned by `GzipRequest.get_route_handler` does differently is convert the `Request` to a `GzipRequest`.

Doing this, our `GzipRequest` will take care of decompressing the data (if necessary) before passing it to our *path operations*.

After that, all of the processing logic is the same.

But if you are certain that the content that you are returning is **serializable with JSON**, you can pass it directly to the response class and avoid the extra overhead that FastAPI would have by passing your return content through the `jsonable_encoder` before passing it to the response class.

{* ../../docs_src/custom_response/tutorial001b_py39.py hl[2,7] *}

/// info

```console
$ pip install httpx
```

///

Import `TestClient`.

Create a `TestClient` by passing your **FastAPI** application to it.

Create functions with a name that starts with `test_` (this is standard `pytest` conventions).

Use the `TestClient` object the same way as you do with `httpx`.

{* ../../docs_src/openapi_callbacks/tutorial001_py310.py hl[33] *}

/// tip

Notice that you are not passing the router itself (`invoices_callback_router`) to `callback=`, but the attribute `.routes`, as in `invoices_callback_router.routes`.

///

### Check the docs { #check-the-docs }