code: func (q *Quantity) String() string {
  	if len(q.s) == 0 {
  		result := make([]byte, 0, int64QuantityExpectedBytes)
  		number, suffix := q.CanonicalizeBytes(result)
  		number = append(number, suffix...)
  		q.s = string(number)
  	}
  	return q.s
  }
docs: // String formats the Quantity as a string, caching the result if not calculated.
  // String is an expensive operation and caching this result significantly reduces the cost of
  // normal parse / marshal operations on Quantity.