Why is clearHighlighting() not returning this?

[hy-net]

clearHighlighting() {
    const attrs = this.getChartState();
    attrs.allNodes.forEach(d => {
        d.data._highlighted = false;
        d.data._upToTheRootHighlighted = false;
    })
    this.update(attrs.root)
    // return this; // to make it consistant
}

[bumbeishvili]

That makes sense