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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 stringReceived(self, response):
 """ Handle a response from the broker. """

        correlation_id = response[0:4]
        try:
            d = self._pending.pop(correlation_id)
        except KeyError:
            self._log.warn((
                "Response has unknown correlation ID {correlation_id!r}."
                " Dropping connection to {peer}."
            ), correlation_id=correlation_id, peer=self.transport.getPeer())
            self.transport.loseConnection()
        else:
            d.callback(response)