code: func NewThrottledBucket(
  	opThrottle Throttle,
  	egressThrottle Throttle,
  	wrapped gcs.Bucket) (b gcs.Bucket) {
  	b = &throttledBucket{
  		opThrottle:     opThrottle,
  		egressThrottle: egressThrottle,
  		wrapped:        wrapped,
  	}
  
  	return
  }
docs: // Create a bucket that limits the rate at which it calls the wrapped bucket
  // using opThrottle, and limits the bandwidth with which it reads from the
  // wrapped bucket using egressThrottle.