如何获得request中传过来的properties属性中的值？

目前在shopify liquid中有一个radio button fieldset，点击每一个选项跳转到一个产品页面，但需要默认该值被选中。
代码如下：
请问checked代码如何实现，(第8行的value_selected如何赋值)？
谢谢！

<style>
  .custom-radio{margin-top:0; display:flex; gap:5px; flex-wrap:wrap}
  .custom-radio div{display:flex;}
  .custom-radio label{margin-bottom:0}
</style>

  {%- liquid
    assign form_id = 'product-form-' | append: section.id
    assign value_selected = request.properties[Header]
  -%}
  {% comment %}
  已经尝试了如下赋值都不好用：
  assign value_selected = properties[Header] 
  assign value_selected = query.properties[Header]
  assign value_selected = params.properties[Header]
  assign value_selected = request.parameters.properties[Header]
  assign value_selected = form.properties[Header]
  assign value_selected = line_item.properties[Header]
  ...
  {% endcomment %}
  
      <form id="{{ form_id }}" action="#" method="GET">
      <fieldset class="js product-form__input product-form__input--pill">
        <legend class="form__label">Header</legend>
				<div class="custom-radio">
            <div>
                <input type="radio" id="Header1" name="properties[Header]" form="{{ form_id }}" value="Header1" 
                {% if value_selected == ‘Header1’ %}checked{% endif %}
                    onchange="document.getElementById('{{ form_id }}').action='/products/p'; 
                    document.getElementById('{{ form_id }}').submit();"
                required>
                <label class="form__label" for="Header1">Header1</label>
            </div>
            <div>
                <input type="radio" id="Header2" name="properties[Header]" form="{{ form_id }}" value="Header2" 
                {% if value_selected == ‘Header2’ %}checked{% endif %}
                    onchange="document.getElementById('{{ form_id }}').action='/products/p'; 
                    document.getElementById('{{ form_id }}').submit();"
                required>
                <label class="form__label" for="Header2">Header2</label>
            </div>
            <div>
                <input type="radio" id="Header3" name="properties[Header]" form="{{ form_id }}" value="Header3" 
                {% if value_selected == ‘Header3’ %}checked{% endif %}
                    onchange="document.getElementById('{{ form_id }}').action='/products/h'; 
                    document.getElementById('{{ form_id }}').submit();"
                required>
                required>
                <label class="form__label" for="Header3">Header3</label>
            </div>
				</div>
      </fieldset>
    <script>
    document.addEventListener("DOMContentLoaded", ()=>{document.querySelector("form[novalidate]").removeAttribute("novalidate")})
    </script>
    </form>