[IMP] using qweb template in _format function instead of return the html part directly

web_widget_radio_tree/static/src/xml/widget.xml

@@ -1,5 +1,8 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <templates>
+    <t t-name="RadioTreeColumn"
+        ><input type="radio" t-att-name="name" t-att="checked" readonly="readonly"></input>
+    </t>
     <t t-name="RadioTree">
         <span class="oe_form_field oe_form_field_boolean oe_form_field_boolean_radio"
               t-att-style="widget.node.attrs.style">