src/vs/workbench/browser/parts/views/treeView.ts/AbstractTreeView/updateCollapseAllToggle
class AbstractTreeView:	private updateCollapseAllToggle() {
		if (this.showCollapseAllAction) {
			this.initializeCollapseAllToggle();
			this.collapseAllToggleContext?.set(!!this.root.children && (this.root.children.length > 0) &&
				this.root.children.some(value => value.collapsibleState !== TreeItemCollapsibleState.None));
		}
	}