print_metric_begin
print_metric_begin(config, evlist, os, aggr_idx);
print_metric_begin(config, evlist, os, aggr_idx);
print_metric_begin(config, evlist, os, aggr_idx);
print_metric_begin(config, evlist, os, /*aggr_idx=*/0);
print_metric_begin(config, evlist, &os, /*aggr_idx=*/0);