new_contents: #!/usr/bin/env python3
  # -*- coding: utf8 -*-
  import json
  
  switches = json.load(open('switches.json', 'r'))
  links = json.load(open('links.json', 'r'))
  hosts = json.load(open('hosts.json', 'r'))
  
  for switch in switches:
      print('{}┐'.format(switch['dpid']))
  
      for port in switch['ports']:
          print('{}├{}'.format(len(switch['dpid']) * ' ', port['port_no']))
  
subject: add ascii topology viewer