How to use the ejs.cache function in ejs

return new Promise((resolve, reject) => {
    try {
      if (this.settings.express.config.trust_proxy) {
        this.app.enable('trust proxy');
      }
      this.app.set('view engine', this.settings.express.views.engine || 'ejs');
      this.app.set('views', path.resolve(this.config.app_root, 'app/views'));
      if (this.settings.express.views.lru_cache) {
        EJS.cache = new LRU(this.settings.express.views.lru);
      }
      this.app.engine('html', EJS.renderFile);
      this.app.engine('ejs', EJS.renderFile);
      if (this.settings.express.views.engine !== 'ejs') {
        this.app.engine(this.settings.express.views.engine, require(this.settings.express.views.package).renderFile);
      }
      resolve(true);
    } catch (e) {
      reject(e);
    }
  });
}

exports.viewSettings = function (options,callback) {

	try{
		let application_settings = options.application_settings;
		let app = options.app;
		let viewengine =  application_settings.templateengine || 'ejs';
		app.set('view engine', viewengine);
		app.set('views', path.resolve(__dirname, '../views'));
		if(application_settings.template_lru_cache===true){
			EJS.cache = LRU(100);
		}
		app.engine('html', EJS.renderFile);
		app.engine('ejs',EJS.renderFile);
		if(application_settings.templatepackage!=='ejs'){
			app.engine(application_settings.templatepackage, require(application_settings.templatepackage).renderFile);
		}


		options.application_settings = application_settings;
		options.app = app;
		callback(null,options);
	}
	catch(e){
		callback(e);
	}
};