@brief Get all orphan collections

`graph._orphanCollections()`

Returns all vertex collections of the graph that are not used in any edge definition.

@EXAMPLES

@EXAMPLE_ARANGOSH_OUTPUT{general_graph__orphanCollections}
  var graph_module = require("@arangodb/general-graph")
~ if (graph_module._exists("myGraph")){var blub = graph_module._drop("myGraph", true);}
  var ed1 = graph_module._relation("myEC1", ["myVC1"], ["myVC2"]);
  var graph = graph_module._create("myGraph", [ed1]);
  graph._addVertexCollection("myVC3", true);
  graph._orphanCollections();
~ var blub = graph_module._drop("myGraph", true);
@END_EXAMPLE_ARANGOSH_OUTPUT