def contexts(self, triple=None):
        default = False
        for c in super(Dataset, self).contexts(triple):
            default |= c.identifier == DATASET_DEFAULT_GRAPH_ID
            yield c
        if not default:
            yield self.graph(DATASET_DEFAULT_GRAPH_ID)
dataset/ETHPy150Open RDFLib/rdflib/rdflib/graph.py/Dataset.contexts/original