abstract protected function build_footer()
This is an abstract method that should be included in the theme-specific layout class that extends Method_Layout. In this method, you'll set up the footer that appears on every page.
For layouts built inside the layout class, this method is called by the build_layout() method, which is called by build_page(). For layouts built directly inside the template, the markup for this method can be returned by using the get_footer_markup() method. In either case, this method should not need to directly be called.
This method accepts no arguments.
This method returns no value. Instead, markup for the footer is added to the
$modals class properties.