def intersection(self, other):
        if not isinstance(other, BaseSet):
            other = Set(other)
        if len(self) <= len(other):
            little, big = self, other
        else:
            little, big = other, self
        common = ifilter(big._data.__contains__, little)
        return self.__class__(common)
group_to_principal formats groups
dataset/ETHPy150Open azoft-dev-team/imagrium/env/Lib/sets.py/BaseSet.intersection--crossover with--dataset/ETHPy150Open mathcamp/pypicloud/tests/test_access_backends.py/TestUtilities.test_group_to_principal