@Override
    public ProfileStep<S> clone() {
        final ProfileStep<S> clone = (ProfileStep<S>) super.clone();
        clone.metrics = null;
        return clone;
    }
Returns {@code Optional.empty()} if traversal is not iterated or if not locked after strategy application.
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/util/ProfileStep.java