Returns the sum of all values in a column

        :param col: column name
        :type col: str
        :return: sum of all the column values
        :rtype: float

        :example: ``sum = ds.sum_("Col 1")``

def sum_(self, col: str) -> float:
        """
        Returns the sum of all values in a column

        :param col: column name
        :type col: str
        :return: sum of all the column values
        :rtype: float

        :example: ``sum = ds.sum_("Col 1")``
        """
        try:
            df = self.df[col]
            num = float(df.sum())
            return num
        except Exception as e:
            self.err(e, "Can not sum data on column " + str(col))