{* ../../docs_src/settings/app02_an_py39/test_main.py hl[9:10,13,21] *}

In the dependency override we set a new value for the `admin_email` when creating the new `Settings` object, and then we return that new object.

Then we can test that it is used.

## Reading a `.env` file { #reading-a-env-file }

    subprocess.run(
        ["git", "config", "user.email", "github-actions[bot]@users.noreply.github.com"],
        check=True,
    )
    branch_name = f"fastapi-topic-repos-{secrets.token_hex(4)}"
    logging.info(f"Creating a new branch {branch_name}")
    subprocess.run(["git", "checkout", "-b", branch_name], check=True)
    logging.info("Adding updated file")
    subprocess.run(["git", "add", str(repos_path)], check=True)

        ["git", "config", "user.email", "github-actions[bot]@users.noreply.github.com"],
        check=True,
    )
    branch_name = f"fastapi-people-sponsors-{secrets.token_hex(4)}"
    logging.info(f"Creating a new branch {branch_name}")
    subprocess.run(["git", "checkout", "-b", branch_name], check=True)
    logging.info("Adding updated file")
    subprocess.run(
        [
            "git",
            "add",

        ["git", "config", "user.email", "github-actions[bot]@users.noreply.github.com"],
        check=True,
    )
    branch_name = f"fastapi-people-contributors-{secrets.token_hex(4)}"
    logging.info(f"Creating a new branch {branch_name}")
    subprocess.run(["git", "checkout", "-b", branch_name], check=True)
    logging.info("Adding updated file")
    subprocess.run(
        [
            "git",
            "add",

    # can create race conditions/deadlocks if the context manager itself
    # has its own internal pool (e.g. a database connection pool)
    # to avoid this we let __exit__ run without a capacity limit
    # since we're creating a new limiter for each call, any non-zero limit
    # works (1 is arbitrary)
    exit_limiter = CapacityLimiter(1)
    try:
        yield await run_in_threadpool(cm.__enter__)
    except Exception as e:

     *
     * @param objectName the name/path of the object
     * @param tags the tags to set
     */
    void setObjectTags(String objectName, Map<String, String> tags);

    /**
     * Ensures the bucket exists, creating it if necessary.
     */
    void ensureBucketExists();

    /**
     * Checks if storage is properly configured and accessible.
     *
     * @return true if storage is available
     */

For example:

{* ../../docs_src/conditional_openapi/tutorial001_py39.py hl[6,11] *}

Here we declare the setting `openapi_url` with the same default of `"/openapi.json"`.

And then we use it when creating the `FastAPI` app.

Then you could disable OpenAPI (including the UI docs) by setting the environment variable `OPENAPI_URL` to the empty string, like:

<div class="termy">

```console
$ OPENAPI_URL= uvicorn main:app

To configure them, pass the `swagger_ui_parameters` argument when creating the `FastAPI()` app object or to the `get_swagger_ui_html()` function.

`swagger_ui_parameters` receives a dictionary with the configurations passed to Swagger UI directly.

    subprocess.run(
        ["git", "config", "user.email", "github-actions[bot]@users.noreply.github.com"],
        check=True,
    )
    branch_name = f"fastapi-people-experts-{secrets.token_hex(4)}"
    logging.info(f"Creating a new branch {branch_name}")
    subprocess.run(["git", "checkout", "-b", branch_name], check=True)
    logging.info("Adding updated file")
    subprocess.run(["git", "add", str(people_path)], check=True)

## An app with callbacks { #an-app-with-callbacks }

Let's see all this with an example.

Imagine you develop an app that allows creating invoices.

These invoices will have an `id`, `title` (optional), `customer`, and `total`.

The user of your API (an external developer) will create an invoice in your API with a POST request.