Convert the main dataframe to html

        :return: html data
        :rtype: str

        :example: ``ds.to_html_()``

def to_html_(self) -> str:
        """Convert the main dataframe to html

        :return: html data
        :rtype: str

        :example: ``ds.to_html_()``
        """
        try:
            renderer = pytablewriter.HtmlTableWriter
            data = self._build_export(renderer)
            return data
        except Exception as e:
            self.err(e, "Can not convert data to html")