src/vs/workbench/api/common/extHostTreeViews.ts/ExtHostTreeViews/$setFocus
class ExtHostTreeViews:	$setFocus(treeViewId: string, treeItemHandles: string) {
		const treeView = this.treeViews.get(treeViewId);
		if (!treeView) {
			throw new Error(localize('treeView.notRegistered', 'No tree view with id \'{0}\' registered.', treeViewId));
		}
		treeView.setFocus(treeItemHandles);
	}