def set_rotation(self, rotation):
        """
        Set the Pie/Doughnut chart rotation: the angle of the first slice.

        Args:
            rotation: First segment angle: 0 <= rotation <= 360.

        Returns:
            Nothing.

        """
        if rotation is None:
            return

        # Ensure the rotation is in Excel's range.
        if rotation < 0 or rotation > 360:
            warn("Chart rotation %d outside Excel range: 0 <= rotation <= 360"
                 % rotation)
            return

        self.rotation = int(rotation)

    ###########################################################################
    #
    # Private API.
    #
    ###########################################################################
dataset/ETHPy150Open jmcnamara/XlsxWriter/xlsxwriter/chart_pie.py/ChartPie.set_rotation/original