@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}
```

<details markdown="1">
<summary>Or use <code>async def</code>...</summary>

If your code uses `async` / `await`, use `async def`:

```Python hl_lines="9  14"
from typing import Union

from fastapi import FastAPI

        able to discuss the full details of what you're working on.


        But Guava aims to provide features that are useful across boundaries of projects, companies,
        or even industries — utilities useful for a sizable proportion of all Java programmers
        everywhere. If you can give enough detail such that any of us can imagine coming across

 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

NOTE:

- `timeToFirstByte` and `timeToResponse` will be expressed in Nanoseconds.
- Additionally in the case of the erasure coded setup `tags.objectLocation` provides per object details about
  - Pool number the object operation was performed on.
  - Set number the object operation was performed on.
  - The list of drives participating in this operation belong to the set.

```json
{
  "version": "1",

                                                <tr
                                                        data-href="${contextPath}/admin/crawlinginfo/details/4/${f:u(data.id)}">
                                                    <td>${f:h(data.sessionId)}</td>
                                                    <td><fmt:formatDate

                                                <tr
                                                        data-href="${contextPath}/admin/dict/mapping/details/${f:u(dictId)}/4/${f:u(data.id)}">
                                                    <td>${f:h(data.inputs)}</td>
                                                    <td>${f:h(data.output)}</td>

                                                <tr
                                                        data-href="${contextPath}/admin/dict/stopwords/details/${f:u(dictId)}/4/${f:u(data.id)}">
                                                    <td>${f:h(data.inputValue)}</td>
                                                </tr>
                                            </c:forEach>

 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

You can combine `dataclasses` with other type annotations in many different combinations to form complex data structures.

Check the in-code annotation tips above to see more specific details.

## Learn More { #learn-more }

You can also combine `dataclasses` with other Pydantic models, inherit from them, include them in your own models, etc.

## Integrated middlewares { #integrated-middlewares }

**FastAPI** includes several middlewares for common use cases, we'll see next how to use them.

/// note | Technical Details

For the next examples, you could also use `from starlette.middleware.something import SomethingMiddleware`.