code: def render_linked_css(self, css_files: Iterable[str]) -> str:
          
          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
          )
docs: 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.