def update_col(self, column_name, series):
        """
        Add or replace a column in the underlying DataFrame.

        Parameters
        ----------
        column_name : str
            Column to add or replace.
        series : pandas.Series or sequence
            Column data.

        """
        logger.debug('updating column {!r} in table {!r}'.format(
            column_name, self.name))
        self.local[column_name] = series