Updated for comments.

            mode = 'a'

        else:

            mode = 'w'

        hdf = io_hdf.HDFDataset(out_path, mode=mode)

        # Cleaner way to do this?

        if nodes:

            for i, n in self.nodes_iter(nodes, data=True):

            for i, n in self.subgraph(nodes).nodes_iter(data=True):

                n.save_features(hdf)

        else:

            for i, n in self.nodes_iter(data=True):

                n.save_features(hdf)

        hdf = None

    def load_features(self, in_path, nodes=[]):

        """

        Load features (keypoints and descriptors) for the