ag-grid react exportMultipleSheetsAsExcel with coulmnKeys

I'm novice in ag-grid react. Currently I want to export the grid data as excel with multiple sheets. The requirement is, export only selected columns(开发者_StackOverflow中文版User will be prompted to choose columns to be present in the excel on click of Export button). I know, we should be using columnKeys attribute. But something, I'm missing here. After clicking columns , I'm getting this error when I click export option

AG Grid: Invalid params supplied to getMultipleSheetsAsExcel() - ExcelExportParams.data is empty.

getRefsFromParent(childRefs) {
    this.setState({
        myRequestedRefs: childRefs
    });

    /* Export multiple sheets commence here  */
    var spreadsheets = []; // var for storing multiple sheets data
    for (let i = 0; i < this.state.checkedSheets.length; i++) {
        if (this.state.checkedSheets[i] == 'Engagements') {
            spreadsheets.push(
                //Referring Engagement Reference passed from Parent Component
                this.state.engRef.current.api.getSheetDataForExcel({
                    sheetName: 'Engagements'
                })
                
            )
        }
        else {
            spreadsheets.push(
                //Sheets will be created based on the selected items from the sheetsList
                this.state.ref.current.api.getSheetDataForExcel({
                    onlySelected: false,
                    sheetName: this.state.checkedSheets[i]
                    
                })
            )
        }
        console.log("Spreadsheets ", spreadsheets);
    }
    this.state.ref.current.api.exportMultipleSheetsAsExcel({
        data: spreadsheets,
        columnKeys: this.state.pickedColumns, //columns selected in the modal by user
        fileName: 'client-details.xlsx',
    });
}