Export “Total” row into excel from ag-grid

I have data in below format in ag-grid and when I try to export to excel all the rows got exported except “Total” row.

product category price1 price2 price3
apple   fruit1    3       4     5
apple   fruit2    6       8     5
carrot  veg1      5       6     9
carrot  veg2      58      25    60
Total             72      43    79

The above data has been grouped by columns on product and category.

I know this is limitation in ag-grid and should be using processRowGroupCallback to include this data. I am not able to achieve this and need some clear examples of how we can achieve this.