/**
* Converts a series to a Point array.
*
+ * @private
* @param {Array.<Array.<(?number|Array<?number>)>} series Array where
* series[row] = [x,y] or [x, [y, err]] or [x, [y, yplus, yminus]].
* @param {boolean} bars True if error bars or custom bars are being drawn.
* to reflect the stacked values.
* @param {string} fillMethod Interpolation method, one of 'all', 'inside', or
* 'none'.
+ * @private
*/
Dygraph.stackPoints_ = function(
points, cumulativeYval, seriesExtremes, fillMethod) {