docs: def _selector_as_string(self, selector):
          """
          Returns a selector as a CSS string
  
          :param selector: A list of tinycss Tokens
          :type selector: list
          :returns: The CSS string for the selector
          :rtype: str
          """
          return ','.join(
              ''.join(token.as_css() for token in strip_whitespace(token_list))
              for token_list in split_on_comma(selector))