docs: public void propertyUnique(P key, String value) {
          GraphTraversal<Vertex, Vertex> traversal = tx().getTinkerTraversal().V().has(key.name(), value);
  
          if (traversal.hasNext()) {
              Vertex vertex = traversal.next();
              if (!vertex.equals(element()) || traversal.hasNext()) {
                  if (traversal.hasNext()) vertex = traversal.next();
                  throw PropertyNotUniqueException.cannotChangeProperty(element(), vertex, key, value);
              }
          }
  
          property(key, value);
      }