src/vs/base/browser/ui/tree/abstractTree.ts/TreeNodeListDragAndDrop/getDragLabel
class TreeNodeListDragAndDrop:	getDragLabel(nodes: ITreeNode<T, TFilterData>[], originalEvent: DragEvent): string | undefined {
		if (this.dnd.getDragLabel) {
			return this.dnd.getDragLabel(nodes.map(node => node.element), originalEvent);
		}

		return undefined;
	}