src/vs/workbench/browser/parts/views/treeView.ts/CustomTreeViewDragAndDrop/handleDragAndLog
class CustomTreeViewDragAndDrop:	private handleDragAndLog(dndController: ITreeViewDragAndDropController, itemHandles: string[], uuid: string, dragCancellationToken: CancellationToken): Promise<IDataTransfer | undefined> {
		return dndController.handleDrag(itemHandles, uuid, dragCancellationToken).then(additionalDataTransfer => {
			if (additionalDataTransfer) {
				const unlistedTypes: string[] = [];
				for (const item of additionalDataTransfer.entries()) {
					if ((item[0] !== this.treeMimeType) && (dndController.dragMimeTypes.findIndex(value => value === item[0]) < 0)) {
						unlistedTypes.push(item[0]);
					}
				}
				if (unlistedTypes.length) {
					this.logService.warn(`Drag and drop controller for tree ${this.treeId} adds the following data transfer types but does not declare them in dragMimeTypes: ${unlistedTypes.join(', ')}`);
				}
			}
			return additionalDataTransfer;
		});
	}