void setDistanceTraversal(final Traversal distanceTraversal) {
        this.distanceTraversal = new PureTraversal<>(this.integrateChild(distanceTraversal.asAdmin()));
    }
@author Daniel Kuppitz (http://gremlin.guru)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/computer/traversal/step/map/ShortestPathVertexProgramStep.java