{
DatasetAccessor du = create() ;
du.putModel(gn1, model1) ;
boolean exists = du.containsModel(gn1) ;
assertTrue(exists) ;
exists = du.containsModel(gn2) ;
assertFalse("Expected gn2 not to exist", exists) ;
Model graph = du.getModel() ;
assertTrue(graph.isEmpty()) ;
graph = du.getModel(gn1) ;