def to_markdown_(self) -> str:
        """Convert the main dataframe to markdown

        :return: markdown data
        :rtype: str

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