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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 _addProteinIdsToGroupMapping(self, proteinIds, groupId):
 """Add a groupId to one or multiple entries of the internal proteinToGroupId mapping. :param proteinIds: a proteinId or a list of proteinIds, a proteinId must be a string. :param groupId: str, a groupId """

        for proteinId in AUX.toList(proteinIds):
            self._proteinToGroupIds[proteinId].add(groupId)