code: def include_theme_files(self, fragment):
          
          theme = self.get_theme()
          if not theme or 'package' not in theme:
              return
  
          theme_package, theme_files = theme.get('package', None), theme.get('locations', [])
          resource_loader = ResourceLoader(theme_package)
          for theme_file in theme_files:
              fragment.add_css(resource_loader.load_unicode(theme_file))
docs: Gets theme configuration and renders theme css into fragment