Symfony：JQuery Collection插件不起作用（无法应用必要的表单主题）

Question

I am trying to build a symfony form with collections, for adding and removing I am trying to use the symfony jquery collection plugin.

To make the plugin work I need to apply a form theme, but not matter what I try the following lines don't work.

                    {% form_theme userSettings 'jquery.collection.html.twig' %}
                    {{ form(userSettings) }}