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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 request_sensor_value(self, req, msg):
 """Request the value of a sensor or sensors. A list of sensor values as a sequence of #sensor-value informs. Parameters name : str, optional Name of the sensor to poll (the default is to send values for all sensors). If name starts and ends with '/' it is treated as a regular expression and all sensors whose names contain the regular expression are returned. Informs ------- timestamp : float Timestamp of the sensor reading in seconds since the Unix epoch, or milliseconds for katcp versions <= 4. count : {1} Number of sensors described in this #sensor-value inform. Will always be one. It exists to keep this inform compatible with #sensor-status. name : str Name of the sensor whose value is being reported. value : object Value of the named sensor. Type depends on the type of the sensor. Returns ------- success : {'ok', 'fail'} Whether sending the list of values succeeded. informs : int Number of #sensor-value inform messages sent. Examples -------- :: ?sensor-value #sensor-value 1244631611.415231 1 psu.voltage 4.5 #sensor-value 1244631611.415200 1 cpu.status off !sensor-value ok 5 ?sensor-value cpu.power.on #sensor-value 1244631611.415231 1 cpu.power.on 0 !sensor-value ok 1 """

        exact, name_filter = construct_name_filter(msg.arguments[0]
                                                   if msg.arguments else None)
        sensors = [(name, sensor) for name, sensor in
                   sorted(self._sensors.iteritems()) if name_filter(name)]

        if exact and not sensors:
            return req.make_reply("fail", "Unknown sensor name.")

        katcp_version = self.PROTOCOL_INFO.major
        for name, sensor in sensors:
            timestamp, status, value = sensor.read_formatted(katcp_version)
            req.inform(timestamp, "1", name, status, value)
        return req.make_reply("ok", str(len(sensors)))