How can i set the modal backdrop static? about angular-modal-service HOT 3 CLOSED

        ModalService.showModal({
                templateUrl: '/modal-campaign-question-editor.html',
                controller: 'CampaignQuestionEditorModalController',
                inputs: {
                    campaign: vm.campaign,
                    currentQuestionInDesignerMode: questionToEdit
                }
            })
            .then(function(modal) {

                //don't allow user to click outside of the modal.
                modal.element.modal({backdrop: 'static'});
                modal.close.then(function (result) {
                    if (result.actionTaken === 'Save') {
                        console.log(result);
                    }

                });
            });