@Override
    public Set<TraverserRequirement> getRequirements() {
        return REQUIREMENTS;
    }
A side-effect step that produces an edge induced subgraph.

@author Stephen Mallette (http://stephen.genoprime.com)
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/sideEffect/SubgraphStep.java