extensions/ipynb/src/serializers.ts/createRawCellFromNotebookCell
function createRawCellFromNotebookCell(cell: NotebookCellData): nbformat.IRawCell {
	const cellMetadata = getCellMetadata(cell);
	const rawCell: any = {
		cell_type: 'raw',
		source: splitMultilineString(cell.value.replace(/\r\n/g, '\n')),
		metadata: cellMetadata?.metadata || {} // This cannot be empty.
	};
	if (cellMetadata?.attachments) {
		rawCell.attachments = cellMetadata.attachments;
	}
	if (cellMetadata?.id) {
		rawCell.id = cellMetadata.id;
	}
	return rawCell;
}