digistore python validate thank you page

digistore_query_valid.py

from hashlib import sha512
from urllib.parse import parse_qs, unquote

def is_digistore_query_valid(qs, thankyou_page_key):
    qs_dict = {key: unquote(value[0]) for key, value in parse_qs(qs).items()}
    expected_sha = qs_dict.pop('sha_sign')
    sha_string = ''
    for key, value in sorted(qs_dict.items()):
        sha_string += f'{key}={value}{thankyou_page_key}'
    m = sha512()
    m.update(sha_string.encode('utf-8'))
    actual_sha = m.digest().hex().upper()
    return actual_sha == expected_sha