old_contents: #!/usr/bin/env python3
  # -*- coding: utf-8 -*-
  import Monitor
  import time
  
  def main():
  
      # show bus lines every 30 seconds
      while True:
          Monitor.print_buses()
          time.sleep(30)
  
  if __name__ == '__main__':
      main()
  
new_contents: #!/usr/bin/python
  # -*- coding: utf-8 -*-
  import Monitor
  import time
  
  
  
  if __name__ == '__main__':
      main()
  
subject: Change from python3 to python, rename main()