def load_unique(self, index_name, key, value, cls):
        index = self.index_manager.get_index(Node, index_name)
        nodes = index.get(key, value)
        if not nodes:
            return None
        if len(nodes) > 1:
            raise LookupError("Multiple nodes match the given criteria; "
                              "consider using `load_all` instead.")
        return self.load(cls, nodes[0])
Load a uniquely indexed node from the database into an object.
dataset/ETHPy150Open nigelsmall/py2neo/py2neo/ext/ogm/store.py/Store.load_unique