def html(self, selector):
        """Return html result that executed by given css selector

        :param selector: `str` css selector
        :return: `list` or `None`
        """

        result = self.__bs4.select(selector)

        return [str(r) for r in result] \
            if result.__len__() > 1 else \
            str(result[0]) if result.__len__() > 0 else None