fixedBarHeight (fixedBarHeight) {
        if (!arguments.length) {
            return this._fixedBarHeight;
        }
        this._fixedBarHeight = fixedBarHeight;
        return this;
    }
Get or set the fixed bar height. Default is [false] which will auto-scale bars.
For example, if you want to fix the height for a specific number of bars (useful in TopN charts)
you could fix height as follows (where count = total number of bars in your TopN and gap is
your vertical gap space).
@example
chart.fixedBarHeight( chartheight - (count + 1) * gap / count);
@param {Boolean|Number} [fixedBarHeight=false]
@returns {Boolean|Number|RowChart}