Write the graph to a gpickle file. Before doing so, serialize and
        include all nodes in their corresponding graph entries.

def write_graph(self, outfile, manifest):
        """Write the graph to a gpickle file. Before doing so, serialize and
        include all nodes in their corresponding graph entries.
        """
        out_graph = _updated_graph(self.graph, manifest)
        nx.write_gpickle(out_graph, outfile)