in src/connectors/sheets-connector.js [127:137]
updateDataList(tabId, newItems, options) {
options = options || {};
let sheets = options.sheets || {};
// If tabId is not specified, use the default Sources tabId.
this.updateDataListExec(tabId, newItems,
(item, rowIndex) => {
// item.sheets.rowIndex in each item is added in getDataList().
return item.sheets.rowIndex;
} /* rowIndexFunc */);
}