hello

I wanted to change the appearance of the default site header in the website template. 
But when I put the Odoo code in an xml page by changing the ID, I get the following error:

odoo.addons.base.models.ir_qweb.QWebException: Error while render the template
ValueError: Element '' cannot be located in parent view
Template: 776
Path: /t/t
Node: 



Part of the code I ran:

xml version="1.0" encoding="utf-8"?>



    id="My_template_header" inherit_id="website.layout" name="My Template Header Default" active="True">
        expr="//header//nav" position="replace">
            t-call="website.navbar">
                t-set="_navbar_classes" t-valuef="shadow-sm"/>
                
id="top_menu_container" class="container justify-content-start justify-content-lg-between">
                    
                    t-call="website.placeholder_header_brand">
                        t-set="_link_class" t-valuef="me-4"/>
                    

Please guide me so that I can change the appearance of header through Odoo template.