build/manage_offer.go
func (m Amount) MutateManageOffer(o interface{}) (err error) {
	switch o := o.(type) {
	default:
		err = errors.New("Unexpected operation type")
	case *xdr.ManageOfferOp:
		o.Amount, err = amount.Parse(string(m))
	case *xdr.CreatePassiveOfferOp:
		o.Amount, err = amount.Parse(string(m))
	}
	return
}
func (m Amount) MutateManageOffer(o interface{}) (err error) {
	switch o := o.(type) {
	default:
		err = errors.New("Unexpected operation type")
	case *xdr.ManageOfferOp:
		o.Amount, err = amount.Parse(string(m))
	case *xdr.CreatePassiveOfferOp:
		o.Amount, err = amount.Parse(string(m))
	}
	return
}
// MutateManageOffer for Amount sets the ManageOfferOp's Amount field