@Override
    public String toString() {
        return StringFactory.propertyString(this);
    }
A utility implementation of a {@link Property} that only has a key but no value and no meta-properties.

@author Stephen Mallette (http://stephen.genoprime.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/structure/util/keyed/KeyedVertexProperty.java