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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 _child_from_reference(self, reference):
 """Returns the child sensor from its reference. Parameters reference : str Reference to sensor (typically its name). Returns ------- child : :class:`katcp.Sensor` object A child sensor linked to one or more aggregate sensors. """

        for child in self._child_to_parents:
            if self._get_sensor_reference(child) == reference:
                return child