public MatchAlgorithm getMatchAlgorithm() {
        if (null == this.matchAlgorithm)
            this.initializeMatchAlgorithm(this.traverserStepIdAndLabelsSetByChild);
        return this.matchAlgorithm;
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/MatchStep.java