rangeChart (rangeChart) {
        if (!arguments.length) {
            return this._rangeChart;
        }
        this._rangeChart = rangeChart;
        this._rangeChart.focusChart(this);
        return this;
    }
Get or set the range selection chart associated with this instance. Setting the range selection
chart using this function will automatically update its selection brush when the current chart
zooms in. In return the given range chart will also automatically attach this chart as its focus
chart hence zoom in when range brush updates.

Usually the range and focus charts will share a dimension. The range chart will set the zoom
boundaries for the focus chart, so its dimension values must be compatible with the domain of
the focus chart.

See the [Nasdaq 100 Index](https://dc-js.github.io/dc.js/) example for this effect in action.
@param {CoordinateGridMixin} [rangeChart]
@returns {CoordinateGridMixin}