def _union(self, other):

        if other.is_ComplexRegion:

            # self in rectangular form
            if (not self.polar) or (not other.polar):
                return ComplexRegion(Union(self.sets, other.sets))

            # self in polar form
            elif self.polar and other.polar:
                return ComplexRegion(Union(self.sets, other.sets), polar=True)

        if self == S.Complexes:
            return self

        return None
dataset/ETHPy150Open sympy/sympy/sympy/sets/fancysets.py/ComplexRegion._union/operator `and` -> `or`