413 Request Entity too Large - how to split up multiple files using python

I have the following code:

    multiple_files = [
    ('reference', (os.path.basename(reference), open(reference, 'rb'), 'application/pdf')),
    ('candidate', (os.path.basename(candidate), open(candidate, 'rb'), 'application/pdf'))
    ]

    payload = {'user': user, 'password': password, 'configname': configname, 'jobid': jobid}

    r = requests.post(url, files=multiple_files, data=payload, verify=False)
 

Each file that I am sending is only about 2Mb. (The code above does work successfully when the files are about 400kb each). When I execute this with the 2Mb files, I get back a 413 error (Request Entity Too Large). I need to change the code as I don't have access to the server to increase the file size.

How would I break up multiple files so that I could send it in chunks?

I've read about how to do it with 1 file, but I can't seem to find how to do it with multiple files.

I tried to change it to this based on somethings I read about streaming uploads:

with open(reference, 'rb') as a, open(candidate, 'rb') as b:
        payload = {'user': user, 
                   'password': password, 
                   'configname': configname, 
                   'jobid': jobid, 
                   'reference': (os.path.basename(reference), a, 'application/pdf'), 
                   'candidate':(os.path.basename(candidate), b, 'application/pdf')
                  }

        r = requests.post(url, data=payload, verify=False)

but that gives a new error: HTTP Status 415 - Unsupported Media Type The server refused this request because the request entity is in a format not supported by the requested resource for the requested method.

So then I tried to add the type to the header

headers = {'content-type': 'application/pdf'}
...
r = requests.post(url, data=payload, headers=headers, verify=False)

But that returned the same 415 Error.

I also tried using another library called requests_toolbelt but that returned the 413 request entity too large as well:

from requests_toolbelt.multipart.encoder import MultipartEncoder
...
    m = MultipartEncoder(
        fields={'user': user,
                'password': password,
                'configname': configname,
                'jobid': jobid,
                'reference': (os.path.basename(reference), open(reference, 'rb'), 'application/pdf'),
                'candidate': (os.path.basename(candidate), open(candidate, 'rb'), 'application/pdf')}
    )

    r = requests.post(url, data=m, headers={'Content-Type': m.content_type}, verify=False)

If anyone can help, it would be much appreciated.

Thanks,