colOrdering (colOrdering) {
        if (!arguments.length) {
            return this._colOrdering;
        }
        this._colOrdering = colOrdering;
        return this;
    }
Get or set a comparator to order the columns.
Default is  {@link https://github.com/d3/d3-array#ascending d3.ascending}.
@param  {Function} [colOrdering]
@returns {Function|HeatMap}