Returns MultiDiGraph from kihs. Nodes are helices and edges are kihs.

def graph(self):
        """ Returns MultiDiGraph from kihs. Nodes are helices and edges are kihs. """
        g = networkx.MultiDiGraph()
        edge_list = [(x.knob_helix, x.hole_helix, x.id, {'kih': x}) for x in self.get_monomers()]
        g.add_edges_from(edge_list)
        return g