how to add "containerCss" in ui-select2

[cred-chirag]

hello, i want to add containerCss: "abc" , in ui-select2 , can you pls suggest,

below demo code are not working,
$scope.select2Options = {
allowClear: false,
containerCss: "abc"
};

    $scope.select2Config = {
        formatResult: $scope.format,
        formatSelection: $scope.format
    };