arangosh> var graph_module = require("org/arangodb/general-graph")
arangosh> var ed1 = graph_module._relation("myEC1", ["myVC1"], ["myVC2"]);
arangosh> var graph = graph_module._create("myGraph", [ed1]);
arangosh> graph._addVertexCollection("myVC3", true);
arangosh> graph._addVertexCollection("myVC4", true);
arangosh> graph._orphanCollections();
[ 
  "myVC3", 
  "myVC4" 
]
arangosh> graph._removeVertexCollection("myVC3");
arangosh> graph._orphanCollections();
[ 
  "myVC4" 
]