code: def inverse(self):
          
          inv = self.__class__()
          inv.add_nodes(self.nodes())
          inv.complete()
          for each in self.edges():
              if (inv.has_edge(each)):
                  inv.del_edge(each)
          return inv
docs: Return the inverse of the graph.
          
          @rtype:  graph
          @return: Complement graph for the graph.