docs: def cookie_decode(data, key, digestmod=None):
      """ Verify and decode an encoded string. Return an object or None."""
      depr(0, 13, "cookie_decode() will be removed soon.",
                  "Do not use this API directly.")
      data = tob(data)
      if cookie_is_encoded(data):
          sig, msg = data.split(tob('?'), 1)
          digestmod = digestmod or hashlib.sha256
          hashed = hmac.new(tob(key), msg, digestmod=digestmod).digest()
          if _lscmp(sig[1:], base64.b64encode(hashed)):
              return pickle.loads(base64.b64decode(msg))
      return None