WriteAPI - Creating a Topic and uploading a file

[KnickKnack]

Hi all,

I'm trying to use the recently introduced WriteAPI to create topics and concurrently upload a file.
I'm doing it via Python and I've already succeeded in create a simple topic without a file using something lilke

        payload = {
            "cid": cid,
            "title": title,
            "content": message
        }

        headers = {
            'Authorization': 'Bearer '+nodebbToken,
            'Content-Type': 'application/json'
        }

        response = requests.request("POST", url, headers=headers, data=json.dumps(payload))

but when it's about files using

        payload = {
            "cid": backstage_cid,
            "title": backstage_title,
            "content": backstage_message
        }        
        headers = {
        'Authorization': 'Bearer '+nodebbToken,
        'Content-Type': 'multipart/form-data'
        }        
        verifySSL = False

        print (payload)

        if (useFile):
            with open(backstage_file, 'rb') as f:
                response = requests.request("POST", url, headers=headers, data=payload, verify=verifySSL, files={backstage_file: f})

it returns
Error: Required parameters were missing from this API call: cid, title, content cause passing the parameters in a plain dictionary rather than a JSON object seems not doable.

The switch from JSON to dictionary is needed otherwise I wouldn't have been able to pass a file together with such header

        headers = {
        'Authorization': 'Bearer '+nodebbToken,
        'Content-Type': 'multipart/form-data'
        }    

Has anybody valuable suggestions here?

Thanks in advance, Riccardo