jdbc-protolib/src/main/java/com/streamsets/pipeline/lib/jdbc/multithread/util/DirectedGraph.java
public Collection<V> getInwardEdgeVertices(V vertex) {
    Collection<V> inwardEdgeVerticesForVertex =  inwardEdgesVertices.get(vertex);
    return inwardEdgeVerticesForVertex != null ? inwardEdgeVerticesForVertex : Collections.<V>emptySet();
  }
public Collection<V> getInwardEdgeVertices(V vertex) {
    Collection<V> inwardEdgeVerticesForVertex =  inwardEdgesVertices.get(vertex);
    return inwardEdgeVerticesForVertex != null ? inwardEdgeVerticesForVertex : Collections.<V>emptySet();
  }
Returns the inward flowing edge vertices.
@param vertex vertex
@return the inward flowing edge vertices.