new_contents: from lauda import StopWatch, stopwatch
  
  def stopwatch_sum_cb(watch, function):
      print ('Time spent {0}'.format(watch.elapsed_time))
  
  @stopwatch(callback=stopwatch_sum_cb)
  def awesome_sum(a, b):
      return a + b
  
  @stopwatch()
  def awesome_mul(a, b):
      return a * b
  
  print awesome_sum(5, 10)
  print awesome_mul(5, 10)
  
  watch = StopWatch()
  watch.start()
  for i in range(10000000):
      pass
  watch.stop()
  print ('Time spent in range {0}'.format(watch.elapsed_time))
  
subject: Add demo.py