old_contents: #!/usr/bin/env python
  
  # make a function that prints 'hello'
  
  def my_func():
      print 'hello'
  
  if __name__ == "__main__":
      my_func()
  
new_contents: #!/usr/bin/env python
  
  # make a function that prints 'hello'
  
  def my_func():
      print 'hello'
  
  def main():
      my_func()
  
  if __name__ == "__main__":
      main()
  
subject: revise my_func.py