rightYAxisLabel (rightYAxisLabel, padding) {
        if (!arguments.length) {
            return this._rightYAxisLabel;
        }
        this._rightYAxisLabel = rightYAxisLabel;
        this.margins().right -= this._rightYAxisLabelPadding;
        this._rightYAxisLabelPadding = (padding === undefined) ? DEFAULT_RIGHT_Y_AXIS_LABEL_PADDING : padding;
        this.margins().right += this._rightYAxisLabelPadding;
        return this;
    }
Set or get the right y axis label.
@param {String} [rightYAxisLabel]
@param {Number} [padding]
@returns {String|CompositeChart}