old_contents: """
  from: <LINK>
  
  <PUZZLE TEXT>
  
  """
  
  def main():
      """Solve the problem!"""
      pass
  
  if __name__ == "__main__":
      main()
  
new_contents: #! python3
  """
  from: <LINK>
  
  <PUZZLE TEXT>
  
  """
  
  def main():
      """Solve the problem!"""
      pass
  
  if __name__ == "__main__":
      main()
  
subject: update template to default to python3