src/vs/workbench/contrib/notebook/browser/notebookEditorWidget.ts/NotebookEditorWidget/moveCellUp
class NotebookEditorWidget:	async moveCellUp(cell: ICellViewModel): Promise<ICellViewModel | null> {
		if (!this.viewModel) {
			return null;
		}

		if (this.viewModel.options.isReadOnly) {
			return null;
		}

		const index = this.viewModel.getCellIndex(cell);
		if (index === 0) {
			return null;
		}

		const newIdx = index - 1;
		return this._moveCellToIndex(index, 1, newIdx);
	}