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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 getVariantAnnotationSet(self, id_):
 """ Returns the AnnotationSet in this dataset with the specified 'id' """

        if id_ not in self._variantAnnotationSetIdMap:
            raise exceptions.AnnotationSetNotFoundException(id_)
        return self._variantAnnotationSetIdMap[id_]