Github user okram commented on the issue:
https://github.com/apache/tinkerpop/pull/705
I don't think it is a good idea to implement `TinkerGraph.clone()`. I
think, instead, that there could be a "clone utility" that works for all
graphs, not just TinkerGraph. E.g.
```
GraphHelper.cloneGraph(original, new)
```
The reasoning of implementing `clone()` just for test cases is weak and
doesn't warrant the semantic confusion that this would entail (as no other
graphs are cloneable).---
