old_contents: """
  Replace all whitespace in a string with '%20'
  """
  
  def replace(string):
      for i in string:
          string.replace("", %20)
      return string
  
new_contents: """
  Replace all whitespace in a string with '%20'
  """
  
  def replace(string):
      return string.replace(' ', '%20')
  
subject: Update 1.4_replace_whitespace.py