Default method used to render the final css links for the
        rendered webpage.

        Override this method in a sub-classed controller to change the output.

def render_linked_css(self, css_files: Iterable[str]) -> str:
        """Default method used to render the final css links for the
        rendered webpage.

        Override this method in a sub-classed controller to change the output.
        """
        paths = []
        unique_paths = set()  # type: Set[str]

        for path in css_files:
            if not is_absolute(path):
                path = self.static_url(path)
            if path not in unique_paths:
                paths.append(path)
                unique_paths.add(path)

        return "".join(
            '<link href="' + escape.xhtml_escape(p) + '" '
            'type="text/css" rel="stylesheet"/>'
            for p in paths
        )