code: public function convert(float $duration, TimeUnit $timeUnit) : float
      {
          return $duration * ($timeUnit->inMicros / $this->inMicros);
      }
docs: Convert the given time duration in the given unit to this unit.
  
  For example, to convert 10 minutes to milliseconds, use: TimeUnit::$MILLISECONDS->convert(10, TimeUnit::$MINUTES)
  
  @param $duration float The time duration in the given sourceUnit
  @param TimeUnit $timeUnit the unit of the sourceDuration argument
  @return float the converted duration in this unit