How to extend a base template for a specific page only, without affecting other pages that use the same base template?


I would like to slightly modify the base page layout for one page. 

So, I created my own template that inherits from portal.frontend_layout:

    <template id="customized_layout" name="Customized Layout for my special page"  inherit_id="portal.frontend_layout">
        .... my code for modifying the default frontend_layout

I call it myself in my own page like this:

<t name="My page" t-name="mypage">
   <t t-call="mymodule.customized_layout">


The problem is that this new template now becomes effective not only for my mypage page, but for all pages that use portal.frontend_layout.

Is there a clean way to make the inheritance work explicitly for a specific page only without overwriting other pages that call the base template, and also without duplicating entire code of the base templates into my own template?