code: def export_kappa_cm(model, fname=None):
      
      from .kappa_util import cm_json_to_graph
      kappa = _prepare_kappa(model)
      cmap = kappa.analyses_contact_map()
      cm = cm_json_to_graph(cmap)
      if fname:
          cm.draw(fname, prog='dot')
      return cm
docs: Return a networkx graph representing the model's Kappa contact map.
  
      Parameters
      ----------
      model : pysb.core.Model
          A PySB model to be exported into a Kappa CM.
      fname : Optional[str]
          A file name, typically with .png or .pdf extension in which
          the CM is rendered using pygraphviz.
  
      Returns
      -------
      npygraphviz.Agraph
          A graph object representing the contact map.