def keys(self):
        return (frozenset(chain(*(node.keys() for node in self.__nodes))) |
                frozenset(chain(*(rel.keys() for rel in self.__relationships))))
(internal) Initialize me with a broker and a locally-unique ID.
dataset/ETHPy150Open nigelsmall/py2neo/py2neo/types.py/Subgraph.keys--crossover with--dataset/ETHPy150Open nlloyd/SubliminalCollaborator/libs/twisted/spread/pb.py/RemoteReference.__init__