old_contents: # -*- coding: utf-8 -*-
  
  def foo():
      return True
  
  def bar():
      return False
  
new_contents: # -*- coding: utf-8 -*-
  
  def foo():
      return True
  
  def bar():
      return False
  
  def baz(x)
      if x:
          return x**2
      elif x == 0:
          return x + 17
      else:
          return x
  
subject: Add baz()