docs: def human_readable_delta(start, end):
      """
      Return a string of human readable time delta.
      """
      start_date = datetime.datetime.fromtimestamp(start)
      end_date = datetime.datetime.fromtimestamp(end)
      delta = end_date - start_date
  
      result = []
      if delta.days > 0:
          result.append('%d days' % (delta.days,))
      if delta.seconds > 0:
          hours = int(delta.seconds / 3600)
          if hours > 0:
              result.append('%d hours' % (hours,))
          minutes = int((delta.seconds - hours * 3600) / 60)
          if minutes:
              result.append('%d minutes' % (minutes,))
          seconds = delta.seconds % 60
          if seconds > 0:
              result.append('%d seconds' % (seconds,))
  
      if result:
          return ', '.join(result)
      return 'super fast'