docs: def get_uhmac(user, secret):
      """Make an unique identifier for the user (stored in the session),
      so it can stay logged between requests.
  
      By hashing a snippet of the current password hash salt, it makes possible
      to automatically logout from all other devices just by changing
      (or refreshing) the password.
      """
      secret = to_bytes(secret)
      key = '|'.join([
          hashlib.sha1(secret).hexdigest(),
          str(user.id),
          get_hash_extract(user.password),
      ])
      key = key.encode('utf8', 'ignore')
      mac = hmac.new(key, msg=None, digestmod=hashlib.sha512)
      mac = mac.hexdigest()[:50]
      uhmac = '{0}${1}'.format(user.id, mac)
      return uhmac