code: public static String presentNanoTime(long nanos) {
  		if (nanos == Long.MAX_VALUE || nanos == Long.MIN_VALUE) {
  			return UNDEF_STRING;
  		}
  		return presentNanoTimePrivate((double) nanos);
  	}
docs: Returns nano-time in human readable form with unit. Number is always from 10 to 9999
  except for seconds that are the biggest unit used. In case of undefined value ({@link Long#MAX_VALUE} or
  {@link Long#MIN_VALUE}) string {@link #UNDEF_STRING} is returned, so it can be used for min/max values as well.
  
  @param nanos time in nanoseconds
  @return human readable time string