old_contents: def fizzbuzz(number):
      answer = []
      if number % 3 == 0:
          answer.append('fizz')
      if number % 5 == 0:
          answer.append('buzz')
      if not answer:
          answer.append(str(number))
      return ' '.join(answer)
  
new_contents: #!/usr/bin/env python
  
  def fizzbuzz(number):
      answer = []
      if number % 3 == 0:
          answer.append('fizz')
      if number % 5 == 0:
          answer.append('buzz')
      if not answer:
          answer.append(str(number))
      return ' '.join(answer)
  
  
  if __name__ == '__main__':
      import sys
  
      if len(sys.argv) != 2:
          print('Usage: fizzbuzz <number>')
          sys.exit(1)
      print(fizzbuzz(int(sys.argv[1])))
  
subject: add main function to fizzbuzz example