def __iter__(self):
        already_seen = set()
        for i in self.base_set:
            val = self.lamda(i)
            if val != already_seen:
                continue
            else:
                already_seen.add(val)
                yield val
dataset/ETHPy150Open sympy/sympy/sympy/sets/fancysets.py/ImageSet.__iter__/operator `in` -> `!=`