```Python hl_lines="5-6"
{!../../docs_src/dependencies/tutorial007.py!}
```

/// tip

You can use `async` or regular functions.

**FastAPI** will do the right thing with each, the same as with normal dependencies.

///

## A dependency with `yield` and `try`

If you use a `try` block in a dependency with `yield`, you'll receive any exception that was thrown when using the dependency.

  public void testRemovalNotification_clear_basher() throws InterruptedException {
    // If a clear() happens close to the end of computation, one of two things should happen:
    // - computation ends first: the removal listener is called, and the cache does not contain the
    //   key/value pair

    int removes = frequency(asList(stimuli), remove);
    if ((!features.contains(IteratorFeature.SUPPORTS_REMOVE) && removes > 1)
        || (stimuli.length >= 5 && removes > 2)) {
      // removes are the most expensive thing to test, since they often throw exceptions with stack
      // traces, so we test them a bit less aggressively
      return;
    }

    int removes = frequency(asList(stimuli), remove);
    if ((!features.contains(IteratorFeature.SUPPORTS_REMOVE) && removes > 1)
        || (stimuli.length >= 5 && removes > 2)) {
      // removes are the most expensive thing to test, since they often throw exceptions with stack
      // traces, so we test them a bit less aggressively
      return;
    }

```

////

//// tab | Python 3.8+

```Python hl_lines="14"
{!> ../../docs_src/body_nested_models/tutorial002.py!}
```

////

## Set types

But then we think about it, and realize that tags shouldn't repeat, they would probably be unique strings.

And Python has a special data type for sets of unique items, the `set`.

Then we can declare `tags` as a set of strings:

        }
      }
      return map.values();
    }

    private ImmutableList<Method> getVisibleMethods(Class<?> cls) {
      // Don't use cls.getPackage() because it does nasty things like reading
      // a file.
      String visiblePackage = Reflection.getPackageName(cls);
      ImmutableList.Builder<Method> builder = ImmutableList.builder();

  }

  public void testPartiallyConstructedManager_transitionAfterAddListenerBeforeStateIsReady() {
    // The implementation of this test is pretty sensitive to the implementation :( but we want to
    // ensure that if weird things happen during construction then we get exceptions.
    final NoOpService service1 = new NoOpService();
    // This service will start service1 when addListener is called.  This simulates service1 being

     */
    @Override
    public String getHostName () {
        /*
         * 2010 - We no longer try a Node Status to get the
         * hostname because apparently some servers do not respond
         * anymore. I think everyone post Windows 98 will accept
         * an IP address as the tconHostName which is the principal
         * use of this method.
         */
        if ( this.hostName.isUnknown() ) {

```Python
q: Annotated[str | None] = None
```

////

//// tab | Python 3.8+

```Python
q: Annotated[Union[str, None]] = None
```

////

Both of those versions mean the same thing, `q` is a parameter that can be a `str` or `None`, and by default, it is `None`.

Now let's jump to the fun stuff. 🎉

## Add `Query` to `Annotated` in the `q` parameter

        }
      }
      return map.values();
    }

    private ImmutableList<Method> getVisibleMethods(Class<?> cls) {
      // Don't use cls.getPackage() because it does nasty things like reading
      // a file.
      String visiblePackage = Reflection.getPackageName(cls);
      ImmutableList.Builder<Method> builder = ImmutableList.builder();