src/vs/base/browser/ui/tree/compressedObjectTreeModel.ts/CompressedObjectTreeModel/getFirstElementChild
class CompressedObjectTreeModel:	getFirstElementChild(location: T | null): ICompressedTreeNode<T> | null | undefined {
		const compressedNode = this.getCompressedNode(location);
		return this.model.getFirstElementChild(compressedNode);
	}