@Override
    public <V> Property<V> property(final String key) {
        return null == this.properties ? Property.<V>empty() : this.properties.getOrDefault(key, Property.<V>empty());
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
tinkergraph-gremlin/src/main/java/org/apache/tinkerpop/gremlin/tinkergraph/structure/TinkerEdge.java