Add one or multiple leading proteins to one or multiple protein
        groups.

        :param proteinIds: a proteinId or a list of proteinIds, a proteinId
            must be a string.
        :param groupIds: a groupId or a list of groupIds, a groupId
            must be a string.

def addLeadingToGroups(self, proteinIds, groupIds):
        """Add one or multiple leading proteins to one or multiple protein
        groups.

        :param proteinIds: a proteinId or a list of proteinIds, a proteinId
            must be a string.
        :param groupIds: a groupId or a list of groupIds, a groupId
            must be a string.
        """
        for groupId in AUX.toList(groupIds):
            self.groups[groupId].addLeadingProteins(proteinIds)
            self._addProteinIdsToGroupMapping(proteinIds, groupId)