def __cmp__(self, other):
        if other < None:
            return -1
        elif isinstance(other, Graph):
            return cmp(self.identifier, other.identifier)
        else:
            # Note if None is considered equivalent to owl:Nothing
            # Then perhaps a graph with length 0 should be considered
            # equivalent to None (if compared to it)?
            return 1
dataset/ETHPy150Open RDFLib/rdflib/rdflib/graph.py/Graph.__cmp__/operator `is` -> `<`