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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 getCallSetByName(self, name):
 """ Returns a CallSet with the specified name, or raises a CallSetNameNotFoundException if it does not exist. """

        if name not in self._callSetNameMap:
            raise exceptions.CallSetNameNotFoundException(name)
        return self._callSetNameMap[name]