old_contents: #  File:       luhn.py
  #  Purpose:    Write a program that can take a number and determine whether
  #              or not it is valid per the Luhn formula.
  #  Programmer: Amal Shehu
  #  Course:     Exercism
  #  Date:       Sunday 18 September 2016, 09:55 PM
  
new_contents: #  File:       luhn.py
  #  Purpose:    Write a program that can take a number and determine whether
  #              or not it is valid per the Luhn formula.
  #  Programmer: Amal Shehu
  #  Course:     Exercism
  #  Date:       Sunday 18 September 2016, 09:55 PM
  
  
  def Luhn(card_number):
  
      digits = digits_of(card_number)
      
  def checksum(card_number):
      return luhn(card_number)
  
subject: Add card verification function