anchor.diff:  
   strategy = new SubgraphStrategy(vertexCriterion, edgeCriterion)
   sg = new StrategyWrappedGraph(g)
  -sg.getStrategy().setGraphStrategy(strategy)
  +sg.setGraphStrategy(strategy)
   
   // all vertices are here
   sg.V().count().next() + " of " + g.V().count().next() + " vertices"
  
positive.code: 
  GraphStrategy strategy = new SubgraphStrategy(vertexCriterion, edgeCriterion);
  StrategyGraph sg = new StrategyGraph(g);
  sg.getStrategy().setGraphStrategy(strategy);
  
  // all vertices are here
  System.out.println("" + sg.V().count().next() + " of " + g.V().count().next() + " vertices");
  
negative.code: ==>PartitionStrategy
  gremlin> sg = new StrategyGraph(g)
  ==>strategywrappedgraph[tinkergraph[vertices:0 edges:0]]
  gremlin> sg.setGraphStrategy(strategy)
  ==>null
  ----
  
  