def _substructures(self, idx):
        children = self._children
        result = []
        todo = [idx]

        while todo:
            result.append(todo.pop())
            todo.extend(children[result[-1]])
        return np.array(result, dtype=np.int)
When the set wasn't mutated, no reflection should take place.
dataset/ETHPy150Open glue-viz/glue/glue/plugins/dendro_viewer/client.py/DendroClient._substructures--crossover with--dataset/ETHPy150Open numba/numba/numba/tests/test_sets.py/TestSetReflection.test_reflect_clean