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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 register_sensor(self, child):
 """Register a sensor required by an aggregate sensor registered with add_delayed. Parameters child : :class:`katcp.Sensor` object A child sensor required by one or more delayed aggregate sensors. """

        child_name = self._get_sensor_reference(child)
        if child_name in self._registered_sensors:
            raise ValueError("Sensor %r already registered with aggregate"
                             " tree" % child)
        self._registered_sensors[child_name] = child
        completed = []
        for parent, (_rule, names, sensors) in \
                self._incomplete_aggregates.iteritems():
            if child_name in names:
                names.remove(child_name)
                sensors.add(child)
                if not names:
                    completed.append(parent)
        for parent in completed:
            rule_function, _names, sensors = \
                self._incomplete_aggregates[parent]
            del self._incomplete_aggregates[parent]
            self.add(parent, rule_function, sensors)