anchor.diff:  ==>neo4jgraph[EmbeddedGraphDatabase [/tmp/neo4j]]
   gremlin> swg = new StrategyWrappedGraph(g)
   ==>defaultgraphstrategy[neo4jgraph[EmbeddedGraphDatabase [/tmp/neo4j]]]
  -gremlin> swg.strategy().setGraphStrategy(IdGraphStrategy.build("idKey").create())
  +gremlin> swg.getStrategy().setGraphStrategy(IdGraphStrategy.build("idKey").create())
   ==>null
   gremlin> swg.addVertex(id,"42a").id()
   ==>42a
  
positive.code: 
  GraphStrategy strategy = new SubgraphStrategy(vertexCriterion, edgeCriterion);
  StrategyWrappedGraph sg = new StrategyWrappedGraph(g);
  sg.strategy().setGraphStrategy(strategy);
  
  // all vertices are here
  System.out.println("" + sg.V().count() + " of " + g.V().count() + " vertices");
  
negative.code: ==>PartitionGraphStrategy
  gremlin> sg = new StrategyWrappedGraph(g)
  ==>strategywrappedgraph[tinkergraph[vertices:0 edges:0]]
  gremlin> sg.getStrategy().setGraphStrategy(strategy)
  ==>null
  ----
  
  