def set_yticks_for_all(self, row_column_list=None, ticks=None):
        """Manually specify the y-axis tick values.

        :param row_column_list: a list containing (row, column) tuples to
            specify the subplots, or None to indicate *all* subplots.
        :type row_column_list: list or None
        :param ticks: list of tick values.

        """
        if row_column_list is None:
            self.ticks['y'] = ticks
        else:
            for row, column in row_column_list:
                self.set_yticks(row, column, ticks)