public default GraphTraversal<S, Vertex> knows(final String personName) {
        return out("knows").hasLabel("person").has("name", personName);
    }
@author Stephen Mallette (http://stephen.genoprime.com)
gremlin-annotations/src/test/resources/org/apache/tinkerpop/gremlin/process/traversal/dsl/SocialNoDefaultMethodsTraversalDsl.java