def vars2tuples(self, orig_g):
        varmap = {}
        for node, data in orig_g.nodes_iter(data=True):
            if 'comp' not in data and node in self and isinstance(node, basestring):
                varmap[node] = (node, (node,))

        nx.relabel_nodes(self, varmap, copy=False)
convert all var nodes to tuple form
dataset/ETHPy150Open OpenMDAO/OpenMDAO-Framework/openmdao.main/src/openmdao/main/depgraph.py/CollapsedGraph.vars2tuples