docs: def check_signature(token, signature, timestamp, nonce):
      """Check WeChat callback signature, raises InvalidSignatureException
      if check failed.
  
      :param token: WeChat callback token
      :param signature: WeChat callback signature sent by WeChat server
      :param timestamp: WeChat callback timestamp sent by WeChat server
      :param nonce: WeChat callback nonce sent by WeChat sever
      """
      signer = WeChatSigner()
      signer.add_data(token, timestamp, nonce)
      if signer.signature != signature:
          from wechatpy.exceptions import InvalidSignatureException
  
          raise InvalidSignatureException()