def format_time(time_):
   """ Returns a formatted time string in the Orders of magnitude (time)

   Args:
      time_: if -1.0 return 'NOT-MEASURED''

   Returns:
      str: formatted time: Orders of magnitude (time)
         second         (s)
         millisecond    (ms)  One thousandth of one second
         microsecond    (µs)  One millionth of one second
         nanosecond     (ns)  One billionth of one second
   """
   if time_ == -1.0:
      final_time_str = 'NOT-MEASURED'
   else:
      base = 1
      for unit in ['s', 'ms', 'us']:
         if time_ >= base:
            break
         base /= 1000
      else:
         unit = 'ns'
      final_time_str = '{:.2f} {}'.format(time_ / base, unit)
   return final_time_str