def _clusterBackward(self, seed, Cluster):
        """Cluster the triple store: from a seed, transitively get all
        properties and objects in backward direction of the arcs.

        :param seed: RDFLib Resource

        :param Cluster: a :class:`~rdfextras.sparql.graph.SPARQLGraph`
            instance, that has to be expanded with the new arcs

        """
        try:
            for (s,p) in self.graph.subject_predicates(seed):

                if not Cluster.graph in (s,p,seed):
                    Cluster.add((s, p, seed))
                    self._clusterBackward(s, Cluster)
                    self._clusterBackward(p, Cluster)

        except:
            pass
dataset/ETHPy150Open RDFLib/rdfextras/rdfextras/sparql/graph.py/SPARQLGraph._clusterBackward/swapped operands of `in`