extensions/ipynb/src/deserializers.ts/getNotebookCellMetadata
function getNotebookCellMetadata(cell: nbformat.IBaseCell): {
	[key: string]: any;
} {
	const cellMetadata: { [key: string]: any } = {};
	// We put this only for VSC to display in diff view.
	// Else we don't use this.
	const custom: CellMetadata = {};
	if (cell['metadata']) {
		custom['metadata'] = JSON.parse(JSON.stringify(cell['metadata']));
	}

	if ('id' in cell && typeof cell.id === 'string') {
		custom.id = cell.id;
	}

	cellMetadata.custom = custom;

	if (cell['attachments']) {
		cellMetadata.attachments = JSON.parse(JSON.stringify(cell['attachments']));
	}
	return cellMetadata;
}