code: def potential_purviews(self, direction, mechanism, purviews=False):
          
          system = self.system[direction]
          return [
              purview for purview in system.potential_purviews(
                  direction, mechanism, purviews)
              if set(purview).issubset(self.purview_indices(direction))
          ]
docs: Return all purviews that could belong to the |MIC|/|MIE|.
  
          Filters out trivially-reducible purviews.
  
          Args:
              direction (str): Either |CAUSE| or |EFFECT|.
              mechanism (tuple[int]): The mechanism of interest.
  
          Keyword Args:
              purviews (tuple[int]): Optional subset of purviews of interest.