Imaplib - скачивание файла с именем на кириллице

import getpass, imaplib, email, os, zipfile, sys
 
#директория, куда будем загрузать файлы
detach_dir = 'C:\\folder'
 
if os.path.isdir(detach_dir) == False:
    os.mkdir(detach_dir);
 
M = imaplib.IMAP4_SSL('imap.yandex.com')
M.login('username', 'password')
M.select()
typ, data = M.search(None, 'FROM', '"username@server.domain"')
 
id_list = data[0].split() # ids is a space separated string
 
#Цикл по всем письмам
for num in id_list:
    typ, data = M.fetch(num, '(RFC822)')
    email_body = data[0][1] # getting the mail content
    mail = email.message_from_bytes(email_body) # parsing the mail content to get a mail object
 
    #Check if any attachments at all
    if mail.get_content_maintype() != 'multipart':
        sys.exit()
 
    # we use walk to create a generator so we can iterate on the parts and forget about the recursive headache
    for part in mail.walk():
        # multipart are just containers, so we skip them
        if part.get_content_maintype() == 'multipart':
            continue
 
        # is this part an attachment ?
        if part.get('Content-Disposition') is None:
            continue
 
        filename = part.get_filename()
        counter = 1
 
        # if there is no filename, we create one with a counter to avoid duplicates
        if not filename:
            filename = 'part-%03d%s' % (counter, 'bin')
            counter += 1
 
        att_path = os.path.join(detach_dir, filename)
 
        #Check if its already there
        if not os.path.isfile(att_path) :
            # finally write the stuff
            fp = open(att_path, 'wb')
            fp.write(part.get_payload(decode=True))
            fp.close()
 
 
M.close()
M.logout()

import base64
 
...
filename = part.get_filename()
        
if filename[:11] == '=?KOI8-R?B?': 
    filename = base64.b64decode(filename[11:]).decode('KOI8-R').decode("utf-8")  
if filename[:10] == '=?UTF-8?B?': 
    filename = base64.b64decode(filename[10:]).decode("utf-8")  
...

import locale
CHARSET = locale.getpreferredencoding(do_setlocale=False)
del locale
 
filename = part.get_filename()
filename, charset = email.header.decode_header(filename)
if charset:
    filename = filename.decode(charset)
else:
    filename = filename.decode(CHARSET)