docs: def setup(self, app):
          """ Setup the plugin from an application. """
          super().setup(app)
  
          if isinstance(self.cfg.template_folders, str):
              self.cfg.template_folders = [self.cfg.template_folders]
  
          else:
              self.cfg.template_folders = list(self.cfg.template_folders)
  
          self.ctx_provider(lambda: {'app': self.app})
          self.env = Environment(debug=app.cfg.DEBUG, **self.cfg)