code: def execute_sql(self, statement):
          
          path = '/archive/{}/sql'.format(self._instance)
          req = archive_pb2.ExecuteSqlRequest()
          req.statement = statement
  
          response = self._client.post_proto(path=path,
                                             data=req.SerializeToString())
          message = archive_pb2.ExecuteSqlResponse()
          message.ParseFromString(response.content)
          if message.HasField('result'):
              return message.result
          return None
docs: Executes a single SQL statement.
  
          :param statement: SQL string
          :return: String response
          :rtype: str