code: func (q *Quantity) Copy() *Quantity {
  	if q.Amount == nil {
  		return NewQuantity(0, q.Format)
  	}
  	tmp := &inf.Dec{}
  	return &Quantity{
  		Amount: tmp.Set(q.Amount),
  		Format: q.Format,
  	}
  }
docs: // Copy is a convenience function that makes a deep copy for you. Non-deep
  // copies of quantities share pointers and you will regret that.