<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def getRnaQuantificationSet(self, id_):
 """ Returns the RnaQuantification set with the specified name, or raises a RnaQuantificationSetNotFoundException otherwise. """

        if id_ not in self._rnaQuantificationSetIdMap:
            raise exceptions.RnaQuantificationSetNotFoundException(id_)
        return self._rnaQuantificationSetIdMap[id_]