Binding Polymer template override lumo theme

Hi there, I create a simple component by following doc https://vaadin.com/docs/v14/flow/polymer-templates/tutorial-template-components.html

however, when I try to include a template theme js file in the template, it overrides whole application’s theme

As long as I remove jsmodule import and tag annotation, the application theme works fine, Any ideas?

Thanks in advance!

Cheers