docs: 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