This can make it a lot easier for your users to **implement their APIs** to receive your **webhook** requests, they might even be able to autogenerate some of their own API code.

/// info

Webhooks are available in OpenAPI 3.1.0 and above, supported by FastAPI `0.99.0` and above.

///

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

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

{* ../../docs_src/body_nested_models/tutorial003_py310.py hl[12] *}

With this, even if you receive a request with duplicate data, it will be converted to a set of unique items.

And whenever you output that data, even if the source had duplicates, it will be output as a set of unique items.

    /**
     * Receives a DCERPC fragment from the remote endpoint
     * @param buf the buffer to receive the fragment data
     * @return the number of bytes received
     * @throws IOException if an I/O error occurs during reception
     */
    protected abstract int doReceiveFragment(byte[] buf) throws IOException;

    /**
     * Sends a DCERPC fragment and receives the response in a single operation

    /** Default response timeout in milliseconds */
    int DEFAULT_RESPONSE_TIMEOUT = 30000;
    /** Default socket timeout in milliseconds */
    int DEFAULT_SO_TIMEOUT = 35000;
    /** Default receive buffer size in bytes */
    int DEFAULT_RCV_BUF_SIZE = 60416;
    /** Default send buffer size in bytes */
    int DEFAULT_SND_BUF_SIZE = 16644;
    /** Default session limit */
    int DEFAULT_SSN_LIMIT = 250;

         - key: "content-type"
           value: "image/*" # match objects with 'content-type', with all values starting with 'image/'

#    notify:
#      endpoint: "https://notify.endpoint" # notification endpoint to receive job status events
#      token: "Bearer xxxxx" # optional authentication token for the notification endpoint
#
#    retry:
#      attempts: 10 # number of retries for the job before giving up

## The normal **FastAPI** app { #the-normal-fastapi-app }

Let's first see how the normal API app would look like before adding the callback.

It will have a *path operation* that will receive an `Invoice` body, and a query parameter `callback_url` that will contain the URL for the callback.

This part is pretty normal, most of the code is probably already familiar to you:

description: Suggest an idea for this project
labels: [ "a:feature", "to-triage" ]
assignees: [ ]
body:
  - type: markdown
    attributes:
      value: |
        Please follow the instructions below.
        We receive dozens of issues every week, so to stay productive, we will close issues that don't provide enough information.

        Please open Android-related issues on [the Android Issue Tracker](https://source.android.com/source/report-bugs)

# `UploadFile` class

You can define *path operation function* parameters to be of the type `UploadFile` to receive files from the request.

You can import it directly from `fastapi`:

```python
from fastapi import UploadFile
```

::: fastapi.UploadFile
    options:
        members:
            - file
            - filename
            - size
            - headers
            - content_type
            - read

        original_route_handler = super().get_route_handler()

        async def custom_route_handler(request: Request) -> Response:
            request = GzipRequest(request.scope, request.receive)
            return await original_route_handler(request)

        return custom_route_handler


app = FastAPI()
app.router.route_class = GzipRoute


@app.post("/sum")

        original_route_handler = super().get_route_handler()

        async def custom_route_handler(request: Request) -> Response:
            request = GzipRequest(request.scope, request.receive)
            return await original_route_handler(request)

        return custom_route_handler


app = FastAPI()
app.router.route_class = GzipRoute


@app.post("/sum")