@Override
    public String toString() {
        return "OperationStats{" +
                "duration=" + duration +
                ", requests=" + requests +
                ", inflight=" + inflight +
                ", targetInflight=" + targetInflight +
                ", exceptions=" + exceptions +
                ", bytesSent=" + bytesSent +
                ", averageLatencyMillis=" + averageLatencyMillis +
                ", minLatencyMillis=" + minLatencyMillis +
                ", maxLatencyMillis=" + maxLatencyMillis +
                ", statsByCode=" + statsByCode +
                '}';
    }
@see #operationAverageLatencyMillis()
@return max latency as milliseconds
vespa-feed-client-api/src/main/java/ai/vespa/feed/client/OperationStats.java