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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def set_querier_mode(self, dpid, server_port):
 """set the datapath to work as a querier. note that you can set up only the one querier. when you called this method several times, only the last one becomes effective."""

        self.dpid = dpid
        self.server_port = server_port
        if self._querier_thread:
            hub.kill(self._querier_thread)
            self._querier_thread = None