code: def dependency_graph(self):
          r
          dtree = nx.DiGraph()
          for propname in self.keys():
              dtree.add_node(propname)
              for dependency in self[propname].values():
                  if dependency in list(self.keys()):
                      dtree.add_edge(dependency, propname)
          return dtree
docs: r"""
          Returns a NetworkX graph object of the dependencies
  
          See Also
          --------
          dependency_list
          dependency_map
  
          Notes
          -----
          To visualize the dependencies, the following NetworkX function and
          settings is helpful:
  
          nx.draw_spectral(d, arrowsize=50, font_size=32, with_labels=True,
                           node_size=2000, width=3.0, edge_color='lightgrey',
                           font_weight='bold')