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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, purviews=False):
 """Override Subsystem implementation using Network-level indices."""

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