I've successfully made a Line Chart using the pointStyle 'rectRounded' but when I attempt to do the same for the Doughnut Chart it only gives me the circle style and I can't seem to alter it.

//ts
public chartLabelsDoughnut: Array<any> = ['Client1','Client2','Client3'];
public chartOptionsDoughnut: any = {
    responsive: true,
    legend: {
        position: 'left',
        labels: {
             usePointStyle: true
        }
    },
};
public chartDatasetsDoughnut: Array<any> = [{data: [78, 16, 6], pointStyle: 'rectRounded'}];

// html
<div class="d-block" style="height: 400px; max-height: 100%;">
    <canvas mdbChart [chartType]="chartDoughnutType" [datasets]="chartDatasetsDoughnut" [labels]="chartLabelsDoughnut" [colors]="chartColorsDoughnut" [options]="chartOptionsDoughnut" [legend]="true">
    </canvas>
</div>