## Pin your `fastapi` version { #pin-your-fastapi-version }

The first thing you should do is to "pin" the version of **FastAPI** you are using to the specific latest version that you know works correctly for your application.

For example, let's say you are using version `0.112.0` in your app.

        assertNotSame(client1, client2);
    }

    // Test constructor with different thread context
    public void test_constructorInDifferentThread() throws Exception {
        // Test that constructor works in different thread
        final CrawlerEngineClient[] clientHolder = new CrawlerEngineClient[1];
        final Exception[] exceptionHolder = new Exception[1];

        Thread thread = new Thread(() -> {
            try {

Do you want to just have a `str`? Or just a `dict`? Or a database class model instance directly? It all works the same way.

You actually don't have users that log in to your application but robots, bots, or other systems, that have just an access token? Again, it all works the same.

As the files `app/routers/users.py` and `app/routers/items.py` are submodules that are part of the same Python package `app`, we can use a single dot `.` to import them using "relative imports".

### How the importing works { #how-the-importing-works }

The section:

```Python
from .routers import items, users
```

means:

* Starting in the same package that this module (the file `app/main.py`) lives in (the directory `app/`)...

Swagger UI will handle it behind the scenes for you, but it needs this "redirect" helper.

///

### Create a *path operation* to test it { #create-a-path-operation-to-test-it }

Now, to be able to test that everything works, create a *path operation*:

{* ../../docs_src/custom_docs_ui/tutorial001.py hl[36:38] *}

### Test it { #test-it }

///

## Declare model attributes { #declare-model-attributes }

You can then use `Field` with model attributes:

{* ../../docs_src/body_fields/tutorial001_an_py310.py hl[11:14] *}

`Field` works the same way as `Query`, `Path` and `Body`, it has all the same parameters, etc.

/// note | Technical Details

{* ../../docs_src/dependencies/tutorial011_an_py39.py hl[22] *}

/// tip

All this might seem contrived. And it might not be very clear how is it useful yet.

These examples are intentionally simple, but show how it all works.

In the chapters about security, there are utility functions that are implemented in this same way.

If you understood all this, you already know how those utility tools for security work underneath.

                "0 */15 * * * ?", // Every 15 minutes
                "0 0 12 * * ?", // Daily at noon
                "0 15 10 ? * MON-FRI" // Weekdays at 10:15
        };

        // Test each pattern and see what actually works
        for (String cron : potentiallyValidCrons) {
            boolean result = validator.isValid(cron, context);
            // Don't assert true/false here, just test that method doesn't throw

)

# Initialize the TensorFlow repository and all dependencies.
#
# The cascade of load() statements and tf_workspace?() calls works around the
# restriction that load() statements need to be at the top of .bzl files.
# E.g. we can not retrieve a new repository with http_archive and then load()
# a macro from that repository in the same file.

        assertEquals("NODE_AVAILABLE", WitnessEventType.NODE_AVAILABLE.toString());
    }

    @Test
    void testEnumValueOf() {
        // Test that valueOf works correctly
        assertEquals(WitnessServiceType.CLUSTER_WITNESS, WitnessServiceType.valueOf("CLUSTER_WITNESS"));
        assertEquals(WitnessServiceType.FILE_SERVER_WITNESS, WitnessServiceType.valueOf("FILE_SERVER_WITNESS"));