Ag grid row span

I want to add aggregation and the calculated value of that column in that same cell.
I’m taking input from dropdown for what type of aggregation i need to apply(sum, average, etc).

 if data == []:
        dff_avg_row = [{}]
        df = df if data is None else pd.DataFrame(data)
        if aggregation == "sum":
            dff_avg_row = df["completedDots"].sum()
        elif aggregation == "average":
            dff_avg_row = df["completedDots"].mean()
        elif aggregation == "count":
            dff_avg_row = df["completedDots"].count()
        elif aggregation == "min":
            dff_avg_row = df["completedDots"].min()
        elif aggregation == "max":
            dff_avg_row = df["completedDots"].max()
        # dff_avg_row["measure_link"] = "Mean"
        sum_dff = aggregation + " " + str(dff_avg_row)
        # dashGridOptions={"pinnedBottomRowData": [str(dff_avg_row)]}
        dashGridOptions={"pinnedBottomRowData": [{"measure_link": aggregation,"initiative_link": "",
                                                  "completedDots": '{sum_dff}', "percent_completion":""}]}
        # grid_options["pinnedBottomRowData"] = dff_avg_row
        return dashGridOptions

by using this code i get NaN.
I’m want to show sum(calculated_sum) . and the want to apply diferent aggregation or diferent columns.