public void setEdgeFilter(final Traversal<Vertex, Edge> edgeFilter) {
        if (!TraversalHelper.isLocalStarGraph(edgeFilter.asAdmin()))
            throw GraphComputer.Exceptions.edgeFilterAccessesAdjacentVertices(edgeFilter);
        this.edgeFilter = edgeFilter.asAdmin().clone();
        ////
        this.edgeLegality = new EnumMap<>(Direction.class);
        this.edgeLegality.put(Direction.OUT, new HashMap<>());
        this.edgeLegality.put(Direction.IN, new HashMap<>());
        this.edgeLegality.put(Direction.BOTH, new HashMap<>());
        if (this.edgeFilter.getEndStep() instanceof RangeGlobalStep && 0 == ((RangeGlobalStep) this.edgeFilter.getEndStep()).getHighRange())
            this.allowNoEdges = true;
        ////
        if (this.edgeFilter.getStartStep() instanceof VertexStep) {
            final VertexStep step = (VertexStep) this.edgeFilter.getStartStep();
            final Map<String, Legal> map = this.edgeLegality.get(step.getDirection());
            if (step.returnsEdge()) {
                if (step.getEdgeLabels().length == 0)
                    map.put(null, 1 == this.edgeFilter.getSteps().size() ? Legal.YES : Legal.MAYBE);
                else {
                    for (final String label : step.getEdgeLabels()) {
                        map.put(label, 1 == this.edgeFilter.getSteps().size() ? Legal.YES : Legal.MAYBE);
                    }
                }
            }
        } else if (this.edgeFilter.getStartStep() instanceof UnionStep) {
            final UnionStep<?, ?> step = (UnionStep) this.edgeFilter.getStartStep();
            for (final Traversal.Admin<?, ?> union : step.getGlobalChildren()) {
                if (union.getStartStep() instanceof VertexStep) {
                    final VertexStep vertexStep = (VertexStep) union.getStartStep();
                    final Map<String, Legal> map = this.edgeLegality.get(vertexStep.getDirection());
                    if (vertexStep.returnsEdge()) {
                        if (vertexStep.getEdgeLabels().length == 0)
                            map.put(null, 2 == union.getSteps().size() ? Legal.YES : Legal.MAYBE);
                        else {
                            for (final String label : vertexStep.getEdgeLabels()) {
                                map.put(label, 2 == union.getSteps().size() ? Legal.YES : Legal.MAYBE);
                            }
                        }

                    }
                }
            }
        }
        final Map<String, Legal> outMap = this.edgeLegality.get(Direction.OUT);
        final Map<String, Legal> inMap = this.edgeLegality.get(Direction.IN);
        final Map<String, Legal> bothMap = this.edgeLegality.get(Direction.BOTH);
        for (final Map.Entry<String, Legal> entry : bothMap.entrySet()) {
            final Legal legal = inMap.get(entry.getKey());
            if (null == legal || legal.compareTo(entry.getValue()) > 0)
                inMap.put(entry.getKey(), entry.getValue());
        }
        for (final Map.Entry<String, Legal> entry : bothMap.entrySet()) {
            final Legal legal = outMap.get(entry.getKey());
            if (null == legal || legal.compareTo(entry.getValue()) > 0)
                outMap.put(entry.getKey(), entry.getValue());
        }
        for (final Map.Entry<String, Legal> entry : outMap.entrySet()) {
            final Legal legal = inMap.get(entry.getKey());
            if (null != legal)
                bothMap.put(entry.getKey(), legal.compareTo(entry.getValue()) > 0 ? legal : entry.getValue());
        }
        if (outMap.isEmpty() && inMap.isEmpty() && bothMap.isEmpty()) { // the edge filter could not be reasoned on
            outMap.put(null, Legal.MAYBE);
            inMap.put(null, Legal.MAYBE);
            bothMap.put(null, Legal.MAYBE);
        }
    }
Set the filter for selecting edges from the source graph.
The edge filter can only access the local star graph (not adjacent vertices).

@param edgeFilter The {@link Traversal} that will generate the legal incident edges of the vertex.
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/computer/GraphFilter.java