old_contents: import numpy as np
  
  print("hello world")
  
  def circumference(r):
      return 2*r*np.pi
new_contents: import numpy as np
  
  print("hello world")
  
  
  def circumference(r):
      return 2*r*np.pi
  
  
  def surface(r):
      return np.pi*r**2
subject: add surface function