<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def addCallSet(self, callSet):
 """ Adds the specfied CallSet to this VariantSet. """

        callSetId = callSet.getId()
        self._callSetIdMap[callSetId] = callSet
        self._callSetNameMap[callSet.getLocalId()] = callSet
        self._callSetIds.append(callSetId)
        self._callSetIdToIndex[callSet.getId()] = len(self._callSetIds) - 1