@Override
    public String toString() {
        return StringFactory.stepString(this, this.traversalPickOptions.getOrDefault(Pick.any, Collections.emptyList()));
    }
A placeholder object used to kick off the first traverser in the union.
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/branch/UnionStep.java