@Override
    public MutableMetrics clone() {
        final MutableMetrics clone = new MutableMetrics();
        copyMembers(clone);
        this.nested.values().forEach(nested -> clone.nested.put(nested.id, ((MutableMetrics) nested).clone()));
        return clone;
    }
Gets a copy of the metrics that is immutable. Once this clone is made, the {@link MutableMetrics} can no
longer be modified themselves. This prevents custom steps that implement {@link Profiling} from adding to
the metrics after the traversal is complete.
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/util/MutableMetrics.java