code: def _check_signature(self, msg_signature, timestamp, nonce, echostr):
          
          signature = get_sha1_signature(self.__token, timestamp, nonce, echostr)
          if not signature == msg_signature:
              raise ValidateSignatureError()
          try:
              return self.__pc.decrypt(echostr, self.__id)
          except DecryptAESError as e:
              raise ValidateSignatureError(e)
docs: 验证签名有效性
  
          :param msg_signature: 签名串，对应URL参数的msg_signature
          :param timestamp: 时间戳，对应URL参数的timestamp
          :param nonce: 随机串，对应URL参数的nonce
          :param echostr: 随机串，对应URL参数的echostr
          :return: 解密之后的echostr
          :raise ValidateSignatureError: 签名无效异常