presto-benchmark/src/main/java/io/prestosql/benchmark/AverageBenchmarkResults.java/AverageBenchmarkResults/addResults
class AverageBenchmarkResults:    @Override
    public BenchmarkResultHook addResults(Map<String, Long> results)
    {
        requireNonNull(results, "results is null");
        for (Entry<String, Long> entry : results.entrySet()) {
            Long currentSum = resultsSum.get(entry.getKey());
            if (currentSum == null) {
                currentSum = 0L;
            }
            resultsSum.put(entry.getKey(), currentSum + entry.getValue());
        }
        resultsCount++;

        return this;
    }