default GraphTraversalSource traversal() {
        return new GraphTraversalSource(this);
    }
Generate a reusable {@link GraphTraversalSource} instance.
The {@link GraphTraversalSource} provides methods for creating {@link GraphTraversal} instances.

@return A graph traversal source
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/structure/Graph.java