@Override
        public GraphTraversalSource traversal(final Graph graph) {
            return innerGraphProvider.traversal(graph);
        }
This class provides a way to intercepts calls to {@link Graph} implementation's {@link GraphProvider} instances.
When {@link #openTestGraph(Configuration)} is called the created object is stored in a list and when tests are
complete the {@link #tryClearGraphs()} is called. When this is called, an attempt is made to close all open graphs.
gremlin-test/src/main/java/org/apache/tinkerpop/gremlin/GraphManager.java