public void start() {
        if (finalized) throw new IllegalStateException("Metrics have been finalized and cannot be modified");
        if (-1 != this.tempTime) throw new IllegalStateException("Internal Error: Concurrent Metrics start. Stop timer before starting timer.");

        this.tempTime = System.nanoTime();
    }
Starts the timer for this metric. Should not be called again without first calling {@link #stop()}.
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/util/MutableMetrics.java