Download file from teams sharepoint using Python 3 throws 403 forbidden

import argparse
import urllib.parse
import os
import requests
from requests.auth import HTTPBasicAuth

auth = HTTPBasicAuth('username', 'password')
headers = {'accept': 'application/json;odata=verbose'}

def download_file(filename):
   filename = filename.strip('/')
    print('Downloading\t'+filename)
    r = requests.get('https://xxx.sharepoint.com/'+"_api/Web/GetFileByServerRelativeUrl('/Shared Documents/Folderunderdocument/"+'filename.csv'+"')/$value", auth=auth, stream=True)
    with open(filename, 'wb+') as f:
        for chunk in r.iter_content(chunk_size=1024): 
            if chunk:
                f.write(chunk)
                f.flush()

if __name__ == '__main__':
      download_file('filename.csv')