How to rewrite response

[Lilihx]

We have APIs that return base64 encoded content.
I want to write a script to decode base64 response, like this.

def on_response(response: httpx.Response, posting: Posting) -> None:
    if response is None or response.status_code != 200:
        return
    r = json.loads(response.content)
    if r["data"] is None or r["data"]["content"] is None:
        return
    resp_decode = base64.b64decode(r["data"]["content"])
    r["data"]["real_content"] = resp_decode
    posting.notify("Content: {}".format(r["data"]["real_content"]))
    response.__setattr__("content", resp_decode)
    return None

But it has an error:
Error running on_response script
property 'content' of 'Response' object has no setter