presto-benchmark/src/main/java/io/prestosql/benchmark/JsonBenchmarkResultWriter.java/JsonBenchmarkResultWriter/JsonBenchmarkResultWriter
class JsonBenchmarkResultWriter:    public JsonBenchmarkResultWriter(OutputStream outputStream)
    {
        requireNonNull(outputStream, "outputStream is null");
        try {
            jsonGenerator = new JsonFactory().createGenerator(outputStream, JsonEncoding.UTF8);
            jsonGenerator.writeStartObject();
            jsonGenerator.writeArrayFieldStart("samples");
        }
        catch (IOException e) {
            throw new UncheckedIOException(e);
        }
    }