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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 getFeatureSet(self, id_):
 """ Returns the FeatureSet with the specified id, or raises a FeatureSetNotFoundException otherwise. """

        if id_ not in self._featureSetIdMap:
            raise exceptions.FeatureSetNotFoundException(id_)
        return self._featureSetIdMap[id_]