public void serialize(@Nonnull Iterable<QueryResult> results, @Nonnull OutputStream out) throws IOException {
JsonGenerator g = jsonFactory.createGenerator(out, JsonEncoding.UTF8);
g.writeStartObject();
g.writeNumberField("timestamp", System.currentTimeMillis() / 1000);
g.writeNumberField("proto_version", STACKDRIVER_PROTOCOL_VERSION);
g.writeArrayFieldStart("data");
for (QueryResult metric : results) {
g.writeStartObject();
g.writeStringField("name", metric.getName());
if (instanceId != null && !instanceId.isEmpty()) {