constructor (parent, chartGroup) {
        super(parent, chartGroup);

        this._keySort = (a, b) => ascending(this.keyAccessor()(a), this.keyAccessor()(b));

        this._charts = {};
        this._chartFunction = lineChart;
        this._chartGroup = chartGroup;
        this._seriesAccessor = undefined;
        this._seriesSort = ascending;
        this._valueSort = this._keySort;

        this._mandatoryAttributes().push('seriesAccessor', 'chart');
        this.shareColors(true);
    }
Create a Series Chart.
@example
// create a series chart under #chart-container1 element using the default global chart group
var seriesChart1 = new SeriesChart("#chart-container1");
// create a series chart under #chart-container2 element using chart group A
var seriesChart2 = new SeriesChart("#chart-container2", "chartGroupA");
@param {String|node|d3.selection} parent - Any valid
{@link https://github.com/d3/d3-selection/blob/master/README.md#select d3 single selector} specifying
a dom block element such as a div; or a dom element or d3 selection.
@param {String} [chartGroup] - The name of the chart group this chart instance should be placed in.
Interaction with a chart will only trigger events and redraws within the chart's group.