Return the absolute paths to "template_name" in the specified app
        If the name does not contain an app name (no colon), an empty list
        is returned.
        The parent FilesystemLoader.load_template_source() will take care
        of the actual loading for us.

def get_template_sources(self, template_name, template_dirs=None):
        """
        Return the absolute paths to "template_name" in the specified app
        If the name does not contain an app name (no colon), an empty list
        is returned.
        The parent FilesystemLoader.load_template_source() will take care
        of the actual loading for us.
        """
        if ':' not in template_name:
            return []
        app_name, template_name = template_name.split(":", 1)
        template_dir = get_app_template_dir(app_name)
        if template_dir:
            return [get_template_path(template_dir, template_name, self)]
        return []