public String getQueryRequiredFields(){
        boolean containsInfo = false;
        QueryString qs = new QueryString();
        if (this.trackingAccountNumber!=null) {
            containsInfo=true;
            qs.add("tracking_account_number", this.trackingAccountNumber);
        }
        if (this.trackingPostalCode!=null){
            qs.add("tracking_postal_code", this.trackingPostalCode);
            containsInfo=true;
        }
        if (this.trackingShipDate!=null){
            qs.add("tracking_ship_date", this.trackingShipDate);
            containsInfo=true;
        }
        if(containsInfo){
            return  qs.toString();
        }
        return "";

    }