Function plot_sparks 

pub fn plot_sparks(
    params: &SparkPlotsParams,
    filename: &str,
    ss: &SeriesStore,
    ds: &Datastore,
    abs_dl_ty: &ChartOutputType,
    rel_dl_ty: &ChartOutputType,
    abs_ul_ty: &ChartOutputType,
    rel_ul_ty: &ChartOutputType,
)