def block_code(self, text, lang):
        """text: unicode text to render"""

        if not lang:
            return self._code_no_lexer(text)

        try:
            lexer = get_lexer_by_name(lang, stripall=True)
        except ClassNotFound:  # lexer not found, use plain text
            return self._code_no_lexer(text)

        formatter = HtmlFormatter()

        return highlight(text, lexer, formatter)
text: unicode text to render