build/manage_offer.go
func (m OfferID) MutateManageOffer(o interface{}) (err error) {
	switch o := o.(type) {
	default:
		err = errors.New("Unexpected operation type")
	case *xdr.ManageOfferOp:
		o.OfferId = xdr.Uint64(m)
	}
	return
}
func (m OfferID) MutateManageOffer(o interface{}) (err error) {
	switch o := o.(type) {
	default:
		err = errors.New("Unexpected operation type")
	case *xdr.ManageOfferOp:
		o.OfferId = xdr.Uint64(m)
	}
	return
}
// MutateManageOffer for OfferID sets the ManageOfferOp's OfferID field