Add a column whith the percentages ratio from a column

        :param col: column to calculate ratio from
        :type col: str
        :param ratio_col: new ratio column name, defaults to "Ratio"
        :param ratio_col: str, optional

        :example: ``ds2 = ds.ratio("Col 1")``

def ratio(self, col: str, ratio_col: str="Ratio"):
        """
        Add a column whith the percentages ratio from a column

        :param col: column to calculate ratio from
        :type col: str
        :param ratio_col: new ratio column name, defaults to "Ratio"
        :param ratio_col: str, optional

        :example: ``ds2 = ds.ratio("Col 1")``
        """
        try:
            df = self.df.copy()
            df[ratio_col] = df[[col]].apply(
                lambda x: 100 * x / float(x.sum()))
            self.df = df
        except Exception as e:
            self.err(e, self.ratio, "Can not calculate ratio")