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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def potential_purviews(self, direction, mechanism):
 """All purviews which are not clearly reducible for mechanism. Args: direction (Direction):
 |CAUSE| or |EFFECT|. mechanism (tuple[int]):
 The mechanism which all purviews are checked for reducibility over. Returns: list[tuple[int]]: All purviews which are irreducible over ``mechanism``. """

        all_purviews = utils.powerset(self._node_indices)
        return irreducible_purviews(self.cm, direction, mechanism,
                                    all_purviews)