Set a datetime index from a column

        :param col: column name where to index the date from
        :type col: str

        :example: ``ds.dateindex("mycol")``

def dateindex(self, col: str):
        """
        Set a datetime index from a column

        :param col: column name where to index the date from
        :type col: str

        :example: ``ds.dateindex("mycol")``
        """
        df = self._dateindex(col)
        if df is None:
            self.err("Can not create date index")
            return
        self.df = df
        self.ok("Added a datetime index from column", col)