java.lang.IllegalArgumentException: Children: duplicate children added parent=Group@63e0a6a9[styleClass=plot-content]
        at javafx.scene.Parent$1.onProposedChange(Parent.java:325)
        at com.sun.javafx.collections.VetoableObservableList.add(VetoableObservableList.java:145)
        at com.sun.javafx.collections.ObservableListWrapper.add(ObservableListWrapper.java:90)
        at javafx.scene.chart.LineChart.dataItemAdded(LineChart.java:196)
        at javafx.scene.chart.XYChart.dataItemsChanged(XYChart.java:423)
        at javafx.scene.chart.XYChart.access$2600(XYChart.java:50)
        at javafx.scene.chart.XYChart$Series$1.onChanged(XYChart.java:1382)
        at com.sun.javafx.collections.ObservableListWrapper.callObservers(ObservableListWrapper.java:78)
        at com.sun.javafx.collections.ObservableListWrapper.add(ObservableListWrapper.java:97)
        at com.sun.javafx.collections.ObservableListWrapper.add(ObservableListWrapper.java:90)
        at ensemble.samples.charts.line.AdvancedStockLineChartSample.plotTime(AdvancedStockLineChartSample.java:146)
        at ensemble.samples.charts.line.AdvancedStockLineChartSample.access$100(AdvancedStockLineChartSample.java:53)
        at ensemble.samples.charts.line.AdvancedStockLineChartSample$1.handle(AdvancedStockLineChartSample.java:75)
        at ensemble.samples.charts.line.AdvancedStockLineChartSample$1.handle(AdvancedStockLineChartSample.java:70)
        at com.sun.scenario.animation.shared.TimelineClipCore.visitKeyFrame(TimelineClipCore.java:196)
        at com.sun.scenario.animation.shared.TimelineClipCore.playTo(TimelineClipCore.java:137)
        at javafx.animation.Timeline.impl_playTo(Timeline.java:163)
        at com.sun.scenario.animation.shared.InfiniteClipEnvelope.timePulse(InfiniteClipEnvelope.java:89)
        at javafx.animation.Animation.impl_timePulse(Animation.java:952)
        at com.sun.scenario.animation.shared.AnimationPulseReceiver.timePulse(AnimationPulseReceiver.java:75)
        at com.sun.scenario.animation.AbstractMasterTimer.timePulseImpl(AbstractMasterTimer.java:357)
        at com.sun.scenario.animation.AbstractMasterTimer$MainLoop.run(AbstractMasterTimer.java:280)
        at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:381)
        at com.sun.javafx.tk.quantum.QuantumToolkit$8.run(QuantumToolkit.java:311)