{* ../../docs_src/settings/app02_an_py310/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 }

> What’s the history of this project? It seems to have come from nowhere to awesome in a few weeks [...]

Here's a little bit of that history.

## Alternatives { #alternatives }

I have been creating APIs with complex requirements for several years (Machine Learning, distributed systems, asynchronous jobs, NoSQL databases, etc), leading several teams of developers.

            logger.info("Skipped creating suggest index: both document and search log suggestions are disabled.");
            return 0;
        }

        final SuggestHelper suggestHelper = ComponentUtil.getSuggestHelper();

        logger.info("Creating new suggest index.");
        suggestHelper.suggester().createNextIndex();

For example:

{* ../../docs_src/conditional_openapi/tutorial001_py310.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

## 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.

### Disable the automatic docs { #disable-the-automatic-docs }

The first step is to disable the automatic docs, as by default, those use the default CDN.

To disable them, set their URLs to `None` when creating your `FastAPI` app:

{* ../../docs_src/custom_docs_ui/tutorial001_py310.py hl[8] *}

### Include the custom docs { #include-the-custom-docs }

Now you can create the *path operations* for the custom docs.

  private static final Comparator<Double> VALUE_COMPARATOR =
      Ordering.<Double>natural().reverse().nullsFirst();

  /**
   * Test that creating one TreeMultimap from another does not copy the comparators from the source
   * TreeMultimap.
   */
  public void testCreateFromTreeMultimap() {

For more commands and examples, including local development,
see [this guide](./platforms/documentation/docs/README.md).

### Creating commits and writing commit messages

The commit messages that accompany your code changes are an important piece of documentation. Please follow these guidelines when creating commits:

* [Write good commit messages.](https://cbea.ms/git-commit/#seven-rules)

UserNameDep = Annotated[str, Depends(get_username, scope="function")]

@app.get("/users/me")
def get_user_me(username: UserNameDep):
    return username
```

## Class Dependencies

Avoid creating class dependencies when possible.

If a class is needed, instead create a regular function dependency that returns a class instance.

Do this:

```python
from dataclasses import dataclass

    public void test_ofNullable_performanceAndMemory() {
        // Test creating many OptionalEntity instances
        for (int i = 0; i < 1000; i++) {
            OptionalEntity<Integer> opt = OptionalUtil.ofNullable(i);
            assertTrue(opt.isPresent());
            assertEquals(Integer.valueOf(i), opt.get());
        }

        // Test creating many empty OptionalEntity instances
        for (int i = 0; i < 1000; i++) {