How can I make the side bar children all collapsible, by default it's a not collapsible?

[AnoopFranc]

I am using this command to create my markdown files
npx vuepress-jsdoc -s ./dist/src -d ./docs -f package --include=\"**/*.(ts|js)\" --exclude=\"test*,**/*.d.ts,**/interfaces.*,**/constants.*\"

it creates a sidebar tree which is of type

sidebarTree: (title?: string) => {
    "/package/": {
        title: string;
        collapsable: boolean;
        children: (string | string[])[];
    }[];
}

but by default collapsible is false. how can I change it?
my .vuepress/config.js
// Add the generated sidebar sidebar: Object.assign({}, {...sidebarTree('Package')}),