How to use the cssselect.parse function in cssselect

def series(css):
            selector, = parse(':nth-child(%s)' % css)
            args = selector.parsed_tree.arguments
            try:
                return parse_series(args)
            except ValueError:
                return None

def specificity(css):
            selectors = parse(css)
            assert len(selectors) == 1
            return selectors[0].specificity()

def repr_parse(css):
            selectors = parse(css)
            for selector in selectors:
                assert selector.pseudo_element is None
            return [repr(selector.parsed_tree).replace("(u'", "('")
                    for selector in selectors]

def get_error(css):
            try:
                parse(css)
            except SelectorSyntaxError:
                # Py2, Py3, ...
                return str(sys.exc_info()[1]).replace("(u'", "('")

def series(css):
            selector, = parse(':nth-child(%s)' % css)
            args = selector.parsed_tree.arguments
            try:
                return parse_series(args)
            except ValueError:
                return None

def specificity(css):
            selectors = parse(css)
            assert len(selectors) == 1
            return selectors[0].specificity()

def get_error(css):
            try:
                parse(css)
            except SelectorSyntaxError:
                # Py2, Py3, ...
                return str(sys.exc_info()[1]).replace("(u'", "('")

def _token_list_matches_tree(self, token_list):
        """
        Returns whether the token list matches the HTML tree

        :param selector: A Token list to check
        :type selector: list of Token objects
        :returns: True if the token list has matches in self.tree
        :rtype: bool
        """
        try:
            parsed_selector = cssselect.parse(
                ''.join(token.as_css() for token in token_list))[0]

            return bool(
                self.tree.xpath(
                    self.xpath_translator.selector_to_xpath(parsed_selector)))
        except:
            # On error, assume the selector matches the tree
            return True